My watch is paired to a broken phone
Apple Watch paired to a broken iPhone. Can I pair it with my new phone somehow?
Hi
As your old iPhone cannot be used, follow the instructions here (under "Erase your Apple Watch") to erase your Apple Watch manually:
Unpair your Apple Watch and iPhone - Apple Support
Then pair it to your new iPhone by following the instructions here, being sure to first update that iPhone to the latest version of iOS and choosing to Restore from Backup if offered the option for your Apple Watch during setup:
Set up your Apple Watch - Apple Support
More information: