Game Won't Work After Switching To Hard Drive

I just got a new external hard drive for my MacBook, I got it because my storage was always full from all the custom content I download for the sims 4. I deleted all my cc/mods, and decided to just uninstall and reinstall the game onto the external hard drive. It worked perfect at first, until I started putting cc into the mods folder. I kept getting a pop up saying there were corrupted files. It kept telling me the corrupted file was a certain piece of cc (that I knew was not corrupted) and every time I removed that piece of cc, it just said a different one was corrupted. I decided to try and repair my game, and now I've messed it up even more. It wouldn't stop verifying the game, the progress bar just stayed in the one spot. So I had to force quit, and restarted my MacBook. It's trying to verify the game again, unsuccessfully. I really don't want to have to reinstall the game again and all the packs. My wifi is super slow, it took over two days to re-download them all the first time, and I feel like it won't fix the problem. I've googled trying to find some answers, nothing. If anyone has any ideas, please let me know! ☹️ I just want to play the sims.