I've been using lightroom for a couple of years. I have a Mac with a WD iCloud and a WD passport. The passport is used to back up everything.
My Mac recently started showing a "storage full" so I bought the WD iCloud. I moved photos to that but discovered that no EOS photos had made it,
When I open an old catalogue I can see the names of the files, but no photos.
What has happened to them?
They are not were LR last referenced them so you need to inform LR where they reside. A number of ways to do this, but you can try the Update Folder Location contextual menu command when clicking on a 'root' folder, then navigate to that folder where it now resides. If you move, rename, delete within LR, it 'knows' you did this but if you do any such work outslide LR, it's confused and has no idea you did this. So do all such edits within LR itself. IOW, you could have used LR to copy the files to the new driver as you did and LR would know where they are.