if it's the case
be; is
もし暇だったら手伝ってほしいんだ。
If you're free, I'd like you to help.
もし私だったらそんなことはしないな。
If it were me, I wouldn't do such a thing.
それが本当だったら信じられない話だ。
If that's true, it's an unbelievable story.