Upgrading to new iPhone
Should the SIM card from my old iPhone be put into my new iPhone before transferring all the data from the old iPhone?
iMac 27″, macOS 11.7
In general, you would take the SIM card out of the old phone and install it in the new phone before you set up the new phone.
However.....If you are in the U.S., new phones.....iPhone 14 and iPhone 15....do not use a SIM card, they use what is known as eSIM.....software, not a physical card.
The eSIM set up normally goes smoothly, but there is always a chance that you may need to get in touch with your carrier for assistance with the setup.