The constitutional qualifications for being president are being a natural-born U.S. citizen, a resident for at least 14 years and over the age of 35. A person can be disqualified by conviction in a Senate impeachment trial, but a criminal conviction does not affect eligibility.
https://www.washingtonpost.com/politics/2023/04/17/can-convicted-felon-run-for-president/
He can become president again even if he’s in prison. And then he can pardon anyone including himself.