@Bluebellflora They both used Mojave. And every other file from my iCloud is still there, even ones from years ago. The migration didn't have any problems, I just think it's so weird that it worked on one computer and not the other. The only difference was the Origin update.
I'll keep looking, but at least I have that one save from a year ago. I'm not too worried about the mods, just missing 4 Sims children ☹️
Thank you so much again for your help, I definitely learned a lot!! And will be backing up my saves on my hard drive from now on, lol