Need help facebook phone verification

I have this very old account that got hacked along time ago it doesnt matter to me cuz i nvr used it BUT i hate the fact that someone used that account for random stuff and ik my username and password but it says i need identiciation throught mobile number and the mobile number of that account was an old mobile number i have and now i dont hve access to it how can i get throught the verification process via mobile phone which is the only option i have so can someone tell me how i can solve this?