I don't know my old Apple ID and password

Sorry to hear this. Please consult the following resources for help in regaining access to your account:

If you've forgotten your Apple ID – Apple Support (UK)

If you have forgotten your Apple ID password – Apple Support (UK)

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