libreria LRC

"since I find several libraries, what happens if I delete them and leave only the one in use."

Then the "one in use" becomes your primary working catalog.

To find the name and location of a Catalog you have open in Lr-Classic go to MENU > Lightroom Menu > Catalog Settings. -Note its full name!

Your screen-clip does not show the full file-names, sizes, and dates, of the .LRCAT catalog files in your system.

.LRCAT Catalog files are databases. Each one is different, possibly indexing different photos. Only you can know if the catalog you are viewing contains all photos you have imported. If that is the case and the "one you use" looks OK, then you can delete others with Mac Finder.

You MUST have regular catalog backups on a separate physical hard-drive.