Samsung Galaxy S Duos 3 (SM-G316MY) Firmware Overview
The archive lists 2 official builds for the Samsung Galaxy S Duos 3 across 1 region (CSC). The newest one is G316MYUHU0AOC1, released March 4, 2015 with Android 4.4.4. It is a feature update on bootloader binary 0: once a phone runs it, firmware with a lower binary can no longer be flashed (how to read a build number).
How to Flash SM-G316MY Firmware
Put the Samsung Galaxy S Duos 3 into Download Mode, load the BL, AP, CP and CSC files into Odin on a Windows PC and press Start. Pick a build with the same or a higher Bit than the one installed — a lower bootloader binary will be rejected.