合ってると思うよ!!ちょっとかたい感じだけど。。
I think it's ok. Japanese can understand you but it sounds a littele bit strange.Because we usually skip subject. If you want to say like a japanese I'd recommend next ones. The meaning is same but if I transelate them to English, it is gonna be `What's that`??
これなに??(very casual)
これは何ですか(polite not very polite)