"How many watches does the dragon have?"
Translation:용은 손목시계를 얼마나 많이 가지고 있습니까?
According to Hello in Korean, "The adverb 많이 may be used to add emphasis." https://www.helloinkorean.com/how-much-how-many-in-korean-2/
As far as I can tell, that doesn't work for a few reasons. 얼만이에요 should be 얼마예요 and combined with 은/는 or 이/가 instead of 을/를, but then you'd be asking how much the dragon's watch costs. I believe that 얼마나 많이 있어요 should work, because in this case you'd be asking how many watches there are in the dragon's belongings/how many does he have. The proposed solution means literally "how many watches does the dragon own?", which might sound a bit too specific in English, but I'm guessing it's the most natural sounding phrase in Korean.