Go to the [InmateAid Inmate Search - By State](https://www.inmateaid.com/inmate-search/) to narrow down where they are and then click the appropriate state to get their ID number.
https://www.inmateaid.com/ask-the-inmate/how-do-i-find-out-my-friends-inmate-number-so-i-can-send-him-money#answer
Accepted Answer Date Created: December 06,2015