If you also need to erase your Apple Watch securely, you can follow these steps to unpair your devices.
Back up your device
Make sure you’ve backed up your device so you can restore your data later.
Tap Settings > General > Transfer or Reset [Device]
Tap Erase All Content and Settings.
If asked, enter your passcode or Apple ID password
Forgotten your passcode or Apple ID password?
Confirm that you want to erase your device
If you have an eSIM, you can choose to erase your eSIM or keep it. If you erase your eSIM, you’ll need to contact your network provider to reactivate your mobile plan.
Wait for your device to be erased
It may take a few minutes to erase your data completely.
If you can't erase your iPhone, iPad or iPod touch
- Find out what to do if you can't remember your passcode for your iPhone, iPad or iPod touch, or your device is disabled.
- If you’ve forgotten your Screen Time passcode, you can reset it. Restoring your device using a backup won't remove the Screen Time passcode.
If you still need help, contact Apple Support.