Do I need to transfer my SIM to the new phone before I transfer the data from my old I Phone?

You can transfer the SIM either before or after the transfer has been completed. I, personally, prefer to transfer the SIM before I begin the transfer of data.

Axel F.

If your new phone is an iPhone 12 or 13 contact your carrier to see if you need a new SIM or an eSIM to use the 5G network.