layniiiiii If you can't see any of the saves at all in-game, even the backups, then there's really nothing else to do here, unfortunately. It sounds like something corrupted the saves, but it's hard to say what, and it doesn't really matter if the saves aren't viable anymore.
I know it doesn't help now, but in the future, it's best to keep your own backups whenever possible, not just the game's backups but your own files preserved at different points in time. And maybe you'd want to periodically save your sims to your library so you could place them in a new save if it came to that.