On your new iPhone, sign in with the same Apple ID you use for your Apple Watch
Keep your Apple Watch and new iPhone close together
On your new iPhone, open the Apple Watch app
Tap Start Pairing
Point your iPhone camera at the animation on your Apple Watch to pair
If prompted, enter the pairing code shown on your iPhone or Apple Watch
Tap Restore from Backup when you see the option during setup
Select the most recent Apple Watch backup
Keep both devices close and on power until the restore finishes
On the new iPhone, follow any prompts to allow notifications, location, and other permissions
After setup completes, confirm the watch face and passcode work
If asked, update watchOS on the Apple Watch and iOS on the iPhone
Verify watch features (calls, messages, notifications, payments) are working on the new phone