Cut and image in many square images

@gtsolid

Did it work or do you still need help?

And another option here too:

//community.adobe.com/t5/photoshop/dividing-big-document-to-smaller-ones/m-p/9311087
// split image into x times y segments and save them as psds;
// 2017, use it at your own risk;

// 2020 - Modified by Stephen Marsh, adding prompts, save alert, saved doc test.

#target photoshop

/* Start Unsaved Document Error Check - Part A: Try */
unSaved();

function unSaved() {
    try {
        activeDocument.path;
        /* Finish Unsaved Document Error Check - Part A: Try */

        /* Main Code Start */

        if (app.documents.length > 0) {
            var originalUnits = app.preferences.rulerUnits;
            app.preferences.rulerUnits = Units.PIXELS;
            // document;
            var myDocument = app.activeDocument;
            var theName = myDocument.name.match(/(.*)\.[^\.]+$/)[1];
            var thePath = myDocument.path;
            var theCopy = myDocument.duplicate("copy", false);

            // Loop the X input prompt until a number is entered
            var theXinput;
            while (isNaN(theXinput = prompt("Enter a whole number:", "3")));
            // Convert decimal input to integer
            var theXtoInteger = parseInt(theXinput);
            // Final result
            var theX = theXtoInteger;

            // Loop the Y input prompt until a number is entered
            var theYinput;
            while (isNaN(theYinput = prompt("Enter a whole number:", "3")));
            // Convert decimal input to integer
            var theYtoInteger = parseInt(theYinput);
            // Final result
            var theY = theYtoInteger;

            // Canvas Division
            var xFrac = myDocument.width / theX;
            var yFrac = myDocument.height / theY;
            // PSD options;
            psdOpts = new PhotoshopSaveOptions();
            psdOpts.embedColorProfile = true;
            psdOpts.alphaChannels = true;
            psdOpts.layers = true;
            psdOpts.spotColors = true;
            // create folder;
            var folderName = thePath + "/" + theName + "_" + theX + "x" + theY;
            if (Folder(folderName).exists === false) {
                Folder(folderName).create()
            }
            // save PSD files;
            for (var n = 1; n <= theY; n++) {
                for (var m = 1; m <= theX; m++) {
                    cropTo((m - 1) * xFrac, (n - 1) * yFrac, m * xFrac, n * yFrac);
                    var theNewName = theName + "_" + bufferNumberWithZeros(m, 3) + "_" + bufferNumberWithZeros(n, 3);
                    theCopy.saveAs((new File(folderName + "/" + "_" + theNewName + ".psd")), psdOpts, true);
                    theCopy.activeHistoryState = theCopy.historyStates[0];
                }
            }
            theCopy.close(SaveOptions.DONOTSAVECHANGES);
            // reset;
            app.preferences.rulerUnits = originalUnits;
        }
        ////// buffer number with zeros //////
        function bufferNumberWithZeros(number, places) {
            var theNumberString = String(number);
            for (var o = 0; o < (places - String(number).length); o++) {
                theNumberString = String("0" + theNumberString)
            }
            return theNumberString
        }
        ////// crop //////
        function cropTo(x1, y1, x2, y2) {
            // =======================================================
            var desc7 = new ActionDescriptor();
            var desc8 = new ActionDescriptor();
            var idPxl = charIDToTypeID("#Pxl");
            desc8.putUnitDouble(charIDToTypeID("Top "), idPxl, y1);
            desc8.putUnitDouble(charIDToTypeID("Left"), idPxl, x1);
            desc8.putUnitDouble(charIDToTypeID("Btom"), idPxl, y2);
            desc8.putUnitDouble(charIDToTypeID("Rght"), idPxl, x2);
            var idRctn = charIDToTypeID("Rctn");
            desc7.putObject(charIDToTypeID("T   "), idRctn, desc8);
            desc7.putUnitDouble(charIDToTypeID("Angl"), charIDToTypeID("#Ang"), 0.000000);
            desc7.putBoolean(charIDToTypeID("Dlt "), false);
            desc7.putEnumerated(stringIDToTypeID("cropAspectRatioModeKey"), stringIDToTypeID("cropAspectRatioModeClass"), stringIDToTypeID("pureAspectRatio"));
            desc7.putBoolean(charIDToTypeID("CnsP"), false);
            executeAction(charIDToTypeID("Crop"), desc7, DialogModes.NO);
        }
        alert('PSD Files saved to: ' + folderName);

        /* Main Code Finish */

        /* Start Unsaved Document Error Check - Part B: Catch */
    } catch (err) {
        alert('An image must be both open and saved before running this script!')
    }
}
/* Finish Unsaved Document Error Check - Part B : Catch */

I found an old script, which could be useful as a basis...

#target photoshop

var doc = app.activeDocument;
var hs = doc.activeHistoryState;
var width = doc.height.value;
var height = doc.height.value;
var cellWidth = width;
var cellHeight = height;
var options = new ExportOptionsSaveForWeb();
    options.format = SaveDocumentType.JPEG;
    options.quality = 100;

var doc = app.activeDocument;
var dname = doc.name.substr(0,doc.name.length-4);
var dir = doc.path.toString()+"/";
var rowShift = true;
var imageWidth = activeDocument.width.as('px');
var imageHeight = activeDocument.height.as('px');

var myRulerUnits = app.preferences.rulerUnits;
app.preferences.rulerUnits = Units.PIXELS;
doc.activeLayer.isBackgroundLayer = false;

doc.resizeCanvas(cellWidth, cellHeight, AnchorPosition.TOPLEFT);

var totalOffset = 0;
var xMovement = 0;

for (var y = 0; y < numberOfRows(); y++)
{
    totalOffset = 0;

    for (var x = 0; x < numberOfCells(); x++)
    {
        if (x == 0)
        {
            xMovement = rowShift;
        }
        else
        {
            xMovement = cellWidth;
        }
        totalOffset += xMovement;
        doc.activeLayer.applyOffset(-(xMovement), 0, OffsetUndefinedAreas.WRAPAROUND);
        saveCell(x,y);
    };
    doc.activeLayer.applyOffset(totalOffset, -(cellHeight), OffsetUndefinedAreas.WRAPAROUND);
    rowShift = !rowShift;
};
function numberOfCells()
{
    var theWidth = imageWidth;

    if (rowShift == true)
    {
        var theWidth = theWidth; 
    }
    return Math.floor(theWidth / cellWidth);
}
function numberOfRows()
{
    return Math.floor(imageHeight / cellHeight);
}
function pad(num, size)
{
    var s = "000000000" + num;
    return s.substr(s.length-size);
}
function saveCell(x, y)
{
    var nname = dname + "_" + pad((x + 1), 2);

    doc.exportDocument (new File(dir + "/" + nname + ".jpg"), ExportType.SAVEFORWEB, options);
}
app.purge(PurgeTarget.HISTORYCACHES);
doc.activeHistoryState = hs;
app.preferences.rulerUnits = myRulerUnits;