それなら
文法の解説は英語です。
用法
それなら literally means "if that's the case." それ meaning "that" refers to the speaker's previous statement or the statement which was just mad by the hearer.
例文
頭が痛いんだけど。それなら、すぐに寝た方がいいよ。
I have an headache. That is why it would be good to sleep soon.
今夜、どこか美味しいレストランで食事したいと思っているんだけど。ああ、それなら、新しく出来た和食レストランに行ってたら?なかなか美味しかったよ。
Tonight, somewhere I planned to go to eat at a delicious restaurant. Aa if that's the case you have to try the new Japanese themed restaurant. It is very delicious.