I would hate to be a secret service agent assigned to protect him. It will take at least 6 unless he chooses solitary. Remember what happened to Dahmer? There will be plenty of guys wanting to build a rep by killing a ex president.
He will be whining for the rest of his life. They will have to listen to it every day.

https://www.palmerreport.com/analysis/what-will-it-be-like-to-have-a-former-president-in-prison/51357/