My Apple Watch is paired with my old iPhone and I unpaired it but it’s asking me for my old iCloud that I don’t remember that password or iCloud account how do I fix that

If you can't remember it:

If you forgot your Apple ID password - Apple Support

and you are the ORIGINAL owner then see the 'Start a support request' section in:

How to remove Activation Lock - Apple Support

You can request an Online Activation Lock Removal here.

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.

Otherwise the watch will be of no use to you.