I cannot change my email address as my previous on is obselete.

I have changed email providers from Big Pond to Gmail. Unfortunately, I did not change it over prior to that happening. Now I cannot login to my Firefox. My new email address is: [redacted] @gmail.com [redacted phone#] If you require further information to verify my identity, please feel free to contact me. Your assistance would be greatly appreciated. Cheers! John Corey