Opening files on new external hard drive - still unresolved

Hi, I have written about this before but still haven't been able to resolve how I access photos I transferred over to new external hard drive. I know it has to do with the catalogue, that the photos that were in a catalogue when they were on the older hard drive are no longer on any catalogue on the new hard drive but I'm unable to fix the problem.

I've tried the Update Folder Location many times but nothing happens. The Find Missing Folder command no longer seems to be available. Somewhere I saw the advice to place the ircat files in the new hard drive so I tried that but nothing happened.

Everything remains perfectly organized and in place when I look at the new hard drive on Finder: under Photographs I have annual folders for each year from 2006 to 2022 and in those annual folders I have all the folders I created by downloading photos during that year. And if I open any of those folders and say I want to open a photo, even using LrC to do so, I can see the photo in question (and all the others). When I say I want to open a photo in LrC it brings up the Copy screen and suddenly all my folders and all my photos are there on the left hand of the screen. If, however, I just copy one photo into its own file and then go back to Library, everything disappears and I'm exactly where I was before, except with that one photo now available to view.

So, does this mean that I have to go through this process and Copy from my new Toshiba hard drive over to the same folder on my Toshiba hard drive, and do this for every single folder from the last 16 years? Copy is defined as copying to a new location and adding to catalogue - but I would be copying to same location and, presumably, finally, adding to catalogue. Is that the onerous solution?

When on this screen, I can also change from Copy to Add and then the destination becomes My Catalog. That seems to be what I need to do but do I need to do it at the level of the folders that actually contain photos, rather than the folders (annual, in my case) that contain folders of photos. It would be simpler if I could just go to the parent folder, Photographs, but there are also only 16 annual folders and adding at that level would be fine. I just don't want to lose the file structure that I've set up on this new Toshiba hard drive, since that was one of the points of putting 16 years worth of photos on this one hard drive.

This is driving me a bit crazy and in my attempts to solve this problem I've now lost 'sight' of the other older hard drive I have connected to this computer. No idea what I did that has caused it to disappear from view under Source on the left hand side, but one problem at a time....