IPhone 3GS 4.1.3 or 4.1.2 any higher?

Can I make my IPhone 3GS (iOS 4.1.3 or 4.1.2) Any higher? It is jailbreaked. Can't seem to find "Software Update" Also, my friend has a 3G and it is currently around 6.1.3? He also used Software Update.

If its jailbreaked then therees no software update

Mixed up the iPhones here.

the 3G can't go to 6.1.3, only up to 4.2.1
the 3GS can go up to 6.1.3.

If your iPhone is jailbroken, you have to restore using iTunes. Then you can update to iOS 6.