Quiz: Which Japanese word is correct?

I went to the fish store to buy some fish. I'm going to buy mackerel to use as an ingredient for tonight's dinner. There are four people in my family, so I'm thinking about how much mackerel to buy. The person at the store who was looking at me asked me a question.

みせの人：サバがほしいんですね？　どれだけひつよう　ですか？

わたし：それを（　　　　）ください

1: ４個/こ

2: ４本/ほん

3: ４尾/び

Please comment below, easily!