This is a tough spot to be in, but there is a potential path forward.
The Bottom Line: Since you don’t have your old device or backup codes, your only remaining option is to try and recover the account through Facebook’s official identity verification process.
These strict security protocols are in place to protect all of your personal content, from private text messages to your photo and video albums.
Before you start, double-check if you are still logged in on another device, like a laptop or tablet, as that would be the easiest way in. If not, you must begin the automated recovery flow from the login page by clicking a link like ‘Try another way’. Follow the prompts indicating you no longer have access to your phone, which should eventually lead to an option to upload a photo of your government-issued ID. Be aware that this process is not instant and can take some time for their team to review, but it is the final method available to prove you are the account owner.
Cheers,
Jeff