New iPhone -

Copying data has nothing to do with your phone number, your SIM determines that.

As long as you move your SIM from your old phone to your new, or get a new SIM from your carrier, you will have the same number.

The SIM from an iPhone 3 will not fit an iPhone 12. You will need to get a new SIM from your carrier. They will provide you with instructions on how to activate that SIM on your current number.

You also can NOT use Quickstart to transfer data from a phone that old.

Good catch on the SIM not fitting, I wasn't paying attention to the first model.

All those years working for Verizon are occasionally good for something!