I didn't unpair my apple watch from my old iPhone and I erased my old iPhone and now it won't pair with my new one.

Unpair and erase your Apple Watch - Apple Support

And read the section "if you don't have your old phone".

Or on the watch, go to setting>General>Reset select "Erase all content and Settings".

i lost old phone and watch is linked to it so cannot get on apple watch to connect it to new phone