How do I unlock my Apple Watch Series 9?

if you mean you forgot the passcode then read

If you forget your Apple Watch passcode - Apple Support

if you mean activation lock 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