I need to change my phone number in Google's My Account.

I performed a Factory Restore on my old phone. I have done this several times before and I know what to prepare prior to do prior to the Restore. I've never had any problems before. However, this particular" time, I couldn't get the text, to reset my password. After too many failed attempts. The phone locked and neither the Manufacturer or the Walmart Prepaid Phone Customer Service Employee were not interested in helping me. The only alternative was. To buy a new phone. Which I did (see info below)

The phone is a: T-MOBILE Family Plan Galaxy J3 Luna Pro.
Now I need to know how to reset my phone number in My Account in case I need to use it for the same reason as everything I mentioned previously.