Hey Lambsy54,
If the update hasn't made any progress, you'll want to force restart to regain control: Force restart iPhone - Apple Support
With force restarting, you may need to restart the process of transferring your data. If the same thing happens, we recommend setting your new iPhone up as a new device first, then updating it. After updating it, you can restore it one more time to transfer your data. Here are guides to help, just in case:
Restore your iPhone, iPad, or iPod to factory settings - Apple Support
Transfer data from your previous iOS or iPadOS device to your new iPhone or iPad - Apple Support
Thanks for using Apple Support Communities.
Take care!