Forgot to deactivate the Find My Phone feature on trade-in iPhone

T-mobile account.

I received a new iPhone 16 and used my old iPhone to transfer all data and settings successfully. Then, following the iPhone instructions, I reset the old iPhone to factory settings.

When boxing up old phone I noticed I was supposed to deactivate the Find My Phone feature on the old phone.

is that still necessary to do? If so how would I do that without screwing up my new iPhone setup?