Did you do a search on internet ?

• https://www.google.com/search?sa=N&num=100&q=os7

What is OS 7 please?

It what context?

It could be the ancient Mac OS 7 from 25 years ago or the Fire OS 7 (is based on Android 9 Pie) for the Amazon Fire tablets ?

FireFox has nothing to do with system O/S. That sounds more like Apple O/S which would require you contact them for support.

Support for a Mac OS from 25 years ago?

Edit ok it appears you were confused with Windows 7 as per your thread at /questions/1389820