My iPhone 4s is on iOS 7.1.2 and I want to upgrade to 9.2 but do I need to backup my files?

I read if youre on an iOS lower than 8 you need to backup your files to upgrade to iOS 8 because they ll be deleted but IIm jumping from 7 to 9, will all my stuff be gone/do i need to save everything on my computer?

Yes if you want everything back from pictures music texts etc

To be on the safe side, make a back up. Better safe than sorry. It's actually a good idea to get in the habit of making regular backups, like every week or every other week.