Need help updating to 17 on Pi 3. Please!

Hey everyone, so I’m totally lost here. I’m using retropie on a pi 3 with Raspbian GNU/Linux 8 (Jessie). I’ve tried updating through Retropie menu and that didn’t work, I’ve tried “check for updates” in Kodi and that didn’t work, how do I get onto v.17? I’m on 16.1 right now.

I did my due diligence looking online but it’s confusing. Thanks so much for the help!