I can't unlock Apple Watch

You can ask apple to remove the activation lock online on this page;

Online Activation Lock Removal Tool.

Or this;

If you can't remember/gain access to the apple id that paired the watch to the phone.Take the watch and it's receipt along with some photo id and any other proof of ownership to an Apple Store and request that they remove the Activation Lock for you.

It would the same Apple ID and Apple ID Password you use for your iPhone and your iCloud/App Store Account.

I cant unlock my applewatch ..I lost my id and password

its an old icloud I had years ago

Then you'll need assistance from Apple directly. They'll require the original purchase receipt with the watch serial number on it.

Use the Get Support button at the top of this page.