Re: ...

@singulariitysims  It's possible that moving the files to your hard drive corrupted them, and in that case, there's nothing you can do.  But it's worth trying again, in a clean user folder, to see whether some of the content is salvageable.

Move the existing Sims 4 folder out of Documents > Electronic Arts and onto your desktop, open the game to spawn a clean folder, and quit.  Move one set of files, and nothing else, from your hard drive to the Tray folder inside the new Sims 4 folder, and see whether that item shows up.  Each saved household or build has several corresponding files, and you can group them together and distinguish between distinct sets by sorting the folder's contents by date.  A single item will have generated all the corresponding files at exactly the same time, which should be unique to that particular item.

You can test however many items you want this way, but the keys are to test one set at a time, and to move fresh copies from your hard drive to your computer.