You can call/write the prison and tell them you need a document notarized. They have procedures in place to help you get that document signed. If that fails, you can send the POA to the inmate via snail mail and wait for them to return it to you.
https://www.inmateaid.com/ask-the-inmate/we-are-trying-to-sell-a-piece-of-property-inherited-by-relative-need-inmate-to-sign-paperwork-how-would-that-work-or-a-power-of-attorney-we-can-not-sell-without-his-signature-or-p-o-a-it-also-has-to-be-notarized#answer
Accepted Answer Date Created: March 31,2022