Put your old iPhone and Apple Watch close together
On the old iPhone, open the Watch app
Tap All Watches
Tap the info button next to your watch
Tap Unpair Apple Watch
Enter your Apple ID password if asked
Set up the new iPhone and sign in with the same Apple ID
Turn on Bluetooth and Wi-Fi on the new iPhone
Make sure the Apple Watch is charged
Turn on the Apple Watch
Hold the watch near the new iPhone
Follow the pairing prompt on the new iPhone
Tap Continue
If the prompt does not appear, open the Watch app on the new iPhone
Tap Start Pairing
Choose Restore from Backup if prompted
Select the most recent backup
Complete the setup steps
Wait for apps and data to sync to the watch