Erase Apple Watch from previous iphone

Unpair and erase your Apple Watch

Or;

From a web browser,sign in to iCloud.com with your Apple ID.

Go to Find iPhone.

Click All Devices at the top of the screen.

Click your Apple Watch.

Click Erase [device]. Select Next until the device is erased.

Click Remove from Account.

Check out this page and it will walk you through it with or without phone. Good luck!

https://9to5mac.com/2021/04/19/how-to-unpair-apple-watch/amp/