My Apple Watch is paired with my old phone that I don’t have I’m trying to pair it with my new phone but it doesn’t let me

If you forgot the watch passcode, see:

If you forgot your Apple Watch passcode - Apple Support

If you forgot the Apple ID password:

If you forgot your Apple ID password - Apple Support

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

How to remove Activation Lock - Apple Support

Here are two ways to unpair your watch if you no longer have the paired iPhone:

• See the 'How to erase your Apple Watch if you don't have your iPhone' section of:

Unpair and erase your Apple Watch - Apple Support

• With a web browser, go to: https://www.iCloud.com and sign in with your Apple ID. Open Find My iPhone and select All Devices (at the top). Then click your Apple Watch, select 'Erase Apple Watch', and select Next until the device is erased. Finally click "X" next to remove your Apple Watch.