Problema al cambiar de ordenador

Hi, thanks for your help, and apologies for my delay in answering.

Please, see my answers in red over your questions:

Where do you store the catalog & the original images? Internal drive or an external drive?

In my new computer, I store the catalogue in the internal drive, but the original images in an external. In the old one, I stored the catalogue and part of the images (the newest) in the internal drive and the rest in an external.

If you have kept the folder path/hierarchy precisely the same on the new one, Lightroom Classic allows you to update the folder locations for all your image & folders, and you won't have to go one at a time.

I haven´t maintained exactly the same folder path in the new computer, although is quite similar. However, Lightroom seems to locate most of my images at the beginning; but unfortunately when I try to look for manually the unlocated folders, LC lost other folders previously found…

In Lightroom Classic, go to Library Module. In the Folders panel on the left, right-click on your folders and click on 'Show parent Folder' to look up the root folder. We are looking for the root folder to help us re-link in one go.

This option (show parent folder) doesn´t appear…

Use the 'Update folder location' to show Lightroom Classic the updated path to your images new machine.

Please, see my second answer.