Also, since Google is free, you can just keep it open forever on the off chance that you miss something (which you almost certainly did), and then like the above person said, just doing it slowly over time. Takes a while but you don’t have to do it all in one sitting.

Though I would recommend getting a personal domain and using that with Proton (or literally anyone else at that point). That way you never have to update emails with services again since you can just port from one provider to another.