Having difficulty in backing up an older iPhone to a newer model

I’m trying to back up my iPhone 11 to an iPhone 13 Pro but on the page to “Transfer your phone number “ the only number I’m offered is that of an old e-Sim card I’ve used in international travel. My SIM card that’s in the new phone is not being recognized although it’s in faded print and “Transfer not supported” is on my screen. What do I do ?