hi, firefox is not working on the windows phone platform at the moment and i know of no ongoing developement in mozilla to change that: Will Firefox work on my mobile device?

please also note, that this is a primarily community-run support forum so it's probably not the right place to request things like platform support (we cannot implement any features & devs won't read here). please use https://input.mozilla.org/feedback for that instead... thank you!

The Windows Phone’s market share reportedly dropped from 3 percent (2014) to 1.7 percent in the third quarter of 2015.

So even if Mozilla could make a version for Windows phone's, is it worthwhile to invest money and effort into it now days, no.