Your firmware is actually er9x but customized by Kevin of RCTankAustralia to be more tank-centric and renamed Tanker9x. You can reflash the Turnigy 9X with a tanker9x firmware from his website but you'll need a programmer for that. Check this out, this is from the rctankaustralia forum,
http://rctanksaustralia.com/forum/viewtopic.php?f=117&t=246. You might be able to work out from the pics especially the mixer how the turret controls are set up. Hope this helps.