Hi Brian. Make sure the number is still active for you be able to transfer. Once the transfer has been processed your account with old service provider will be deactivated.

Provide either one of the three pieces of account information from your old service provider – Old Account #, ESN / IMEI / MEID, PIN along with your alternate phone number and your name.

Go to Public Mobile self serve page. Go to "Plan and Add-ons" from home page and "Change Phone number" and continue with the steps above. Or in this case, since you're transferring, you will go through the transfer when activating the SIM.

Source: 1, 2, 3

yes need to ask telus for number transfer