How long are you going to stay here?

你要在这儿停留多久?

Only two days. I'm going to visit a relative.

只待两天，我要探亲。

How long are you going to stay here?

你要在这儿停留多久?

How long do you plan to stay here?

你打算在这里待多久?

I will stay in the States for about a month.

我将在美国停留1个月。