Hi!
Maybe there is a way to change track using System Admin Pro and if so I don't know it but what I would do next is run
https://upgrades.freepbxdistro.org/stable/10.13.66/upgrade-10.13.66-1.sh
see http://wiki.freepbx.org/display/PPS/FreePBX-Distro-6.12.65
As they say on that web page "This will take your 6.12.65 version system to a 10.13.66-1 version and track".
After that System Admin Pro should offer you the updates of that distro so you could update from there or by running the scripts from http://wiki.freepbx.org/display/PPS/FreePBX-Distro-10.13.66 (personally I prefer to do it that way, I have had better luck updating that way).
I would suggest you make a backup before doing anything else though...
Good luck and have a nice day!
Nick