When Thranduil tells Legolas to go north, what did he mean?

At the end of the third Hobbit movie, I recall Thranduil telling Legolas to go north to look for Aragorn. They were at Erebor, and north of that was just the Iron Hills and Forodwaith. Aragorn would not be north of the Wood-elven Kingdom either. What did he mean? Am I misunderstanding the scene?