If you're setting up an iPhone or iPad (Wi-Fi + Cellular), you might need to insert the iPhone SIM card or the iPad SIM card first. You may also be asked to activate the eSIM. Get help if you can't connect to a Wi-Fi network or if you can't activate your iPhone. Take the SIM card out of your current iPhone and place it in the new one before starting the transfer.
The iPhone doesn't store data on the SIM. You can remove the SIM from an old iPhone and activate a new iPhone with the SIM and then move on. Usually when setting it up for the first time. You can insert it at any time during setup.
However, it will request its activation at some point.