Personally I’d rather C3PO’s memories not be restored at all. Someone posted a mock-up a ways back and it definitely needed some work but showed promise.
Imo, it’s more unbelievable that they WOULDN’T have backups of 3PO’s memories. He’s a droid. I’m sure everyone here maintains up-to-date backups of their computers and/or phones, so why would droids in Star Wars be treated any differently?