Don’t know where to go next? At any level just swing by Stormwind, Darnassus, Ironforge or Exodar for Alliance near the business districts of the city are Hero’s Call Boards. They will give you level appropriate quests to go to a zone where it is level appropriate for you to quest.
For you on the Horde side of things the Horde Cities have the equivalent called the Warchief’s Command Boards.
So now the easy answer is go to the Boards to see where you should go. (& as a tip they sometimes have different offerings on different continents). These boards work all the way up to level 85. So have fun questing.