Finally found the plugin I was looking. It is called called Swift Tabs. Every other application I use provides the flexibility to change the next previous tab keys, and even though I had the option, the defaults for everything was always ALT and the arrow keys. I just got used to it and it works well and makes sense. Well, I finally found the firefox plugin that let me change the shortcuts for next/prev tab. Here’s the link

https://addons.mozilla.org/firefox/380/