First and second stimulus payments never received. What should I do now?

Hello!

 

My husband is currently incarcerated, he filed a 1040 paper form in 2019 within the deadline but never received the payments. Can he claim a recovery rebate credit by filing a 2020 form 1040 ? If yes, How should he fill it out ? He had no revenue in 2020. Should he file one form or two (one for each stimulus payment) ?  Thank you for your help!