Fetching details from the dictionary...

if that's the case ...; if so ...; that being the case ...
時間がないのなら、それなら明日にしよう。
If there's no time, then let's do it tomorrow.
雨が降るなら、それなら家にいよう。
If it's going to rain, then let's stay home.
それなら最初から言ってくれればよかったのに。
If so, you should have told me from the beginning.