"How many apples do you have?"
Translation:Quante mele hai?
The subject isn't really used in questions; when it is it's usually put at the beginning, e.g. "Tu quante mele hai?", and sometimes at the end after a comma, e.g. "Quante mele hai, tu?". Putting the subject in the middle is common in some dialects though, e.g. Florentine ("i'che tu fai?", what are you doing?).