upload back up from an old firefox login that is no longer available

My old login email is no longer accessible, I was able to save a backup from my laptop as it is still logged in with the old email. I have a new computer that I downloaded fire fox onto but when I tried to log in, it sent a pass code to my old address, which I no longer have access to. I was told to delete the fire fox off my new computer and reinstall and sign up with a new ID using my new email address. I tried this but my new computer somehow still sees that I had downloaded fire fox previously and wants me to sign in with my old email. I tried setting up a new profile, but it still wants to log in with my old email.