My Apple ID email is an old email I don’t use anymore?

Please see Change your Apple ID - Apple Support

As noted in that page you need to sign out of iCloud and anything else using the old ID (except the device you are using to change it, of course, and even there sign out of iTunes and iCloud) as you will run into problems if you don't. Your synced data will disappear but will re-appear when you sign back in (give it time).