Your inmate will not know automatically. The phone account is set up on your end, and getting the new number to them requires a direct communication since you have not been in contact since the transfer.
The most practical solution is a letter, and InmateAid makes that easy. Email aid@inmateaid.com and ask for a notification coupon code. InmateAid provides these at no charge specifically for situations like this, where you need to get a new phone number to your inmate quickly after setting up service. The letter goes out through InmateAid's standard mail process and arrives at the new facility within about a week.
In that letter, include the new number clearly and ask your inmate to add it to their approved call list at the facility as soon as possible. Once it is on the approved list and they dial it, the call forwards directly to your phone at the discounted rate.
It is worth including a brief note alongside the number so the letter feels personal rather than purely informational. Your inmate has been through a transfer, which means a communication blackout and a disorienting intake process at a new facility. Hearing from you in any form right now matters beyond just the practical information you are sending. Reach out to aid@inmateaid.com today and get that letter moving.