At first, you should say, はい、売っています to reply to my question, then you can say, 団子が欲しかったらMAIDOに行かなくちゃいけない or 団子が食べたくなったらMAIDOに行かなくちゃ! or 団子が欲しいならMAIDOに行く必要があります, etc. Does that make sense?
I thought you meant, “はい、MAIDOに売っております。” The question is, “Does MAIDO sell dangos?” so if you say, “Yes, I’m going to MAIDO,” the answer is a little odd.