I forgot my Apple ID password for my watch

How to pair your Apple Watch with a new iPhone - Apple Support

if your issue is activation lock to an appleID unknown to you then

activation lock is not a thing on the watch it's a theft protection on apples servers

it needs to be removed

About Activation Lock on your

Apple Watch - Apple Support

if you don't know your appleID password If you have

forgotten your Apple ID

password – Apple Support (UK)

then you will need the assistance of apple Activation Lock - Support

(apple.com)

and or

 Apple Support

And or

 Contact - Official Apple Support

and or

Genius Bar Reservation and Apple

Support Options - Apple

The Apple ID for your watch is likely to be the same as the Apple ID you used on the iPhone you used to setup the watch. If you still have the original iPhone in working condition you should be able to reset its Apple ID password to something you know.

There is usually no reason why you should need to use a new Apple ID just because you have a new iPhone. Most times you would want to setup on the same ID as your old iPhone so all your data gets continued. The only common exception I can imagine for this would be when someone is escaping an abusive relationship and needs a clean start.

Change your Apple ID password - Apple Support