"How many watches does the dragon have?"
Translation:용은 손목시계를 얼마나 많이 가지고 있습니까?
가지다 is "to possess" (so the dragon actually has the watches on him - as opposed to just owning some watches).
But since the english doesn't say the dragon has the watches on him, shouldn't 많이 가지다 be unecessary?
Only with 가지고, not the 많이. 가지고 means that the subjest has the objects on his or her possesion on than moment. Like saying "I brought my book (came with it)" 저는 책을 가지고 왔어요