Play Sims 4 on new PC (using external hard drive)

@djmiele65  Sorry for the late reply.  First of all, the game won't read anything inside the second saves folder in your screenshot.  So if your missing saves are in there, you'll need to move them into the main saves folder.

Second of all, OneDrive is syncing your files, and in fact it was in the process when you took this screenshot.  (That's the blue arrows icon.  A green check mark means a file or folder is synced, and a red X means it could not be.)  This isn't necessarily a problem on its own, but OneDrive can definitely interfere with Sims 4 content, so it's better to block auto-syncing, at least until you get everything else sorted out.  You can deselect Documents for syncing:

https://support.microsoft.com/en-us/office/choose-which-onedrive-folders-to-sync-to-your-computer-98b8b011-8b94-419b-aa95-a14ff2415e85

You may first need to pause or cancel the current sync:

https://support.microsoft.com/en-au/office/how-to-cancel-or-stop-sync-in-onedrive-4885c27e-3d89-4d69-be75-2646c71367d3

Or if you have no use for OneDrive, just unlink your computer:

https://support.microsoft.com/en-us/office/turn-off-disable-or-uninstall-onedrive-f32a17ce-3336-40fe-9c38-6efb09f944b0

Once that's addressed, make sure the saves are in the proper saves folder and see whether they'll load.  If not, please post another screenshot just like this one.