Resurrection after iPhone SE fails

My iPhone SE has, after being on the blink for a while, completely given up and cannot power up. I have bought an iPhone XR to replace it.

How can I restore the iTunes backup from my iPhone SE onto my new XR? I have already removed the iPhone SE from iCloud and Find my iPhone, but I keep getting an error in iTunes saying I must turn off Find my iPhone on the SE before I can proceed. Seems like a catch 22 - any suggestions?