你不用知道 的英文是什么?

you don't need to know
也可以说
it's none of your business.

you don't need to know

none of your business

直译
it's not necessary for you to know it.
比较符合口语习惯的译法
you don't need to know

You needn't know it.

直译：
You don't need to know.
严肃点的：
It's none of your business.
I don't think you need to know this.
Why you want to know this?
委婉的：
I am sorry but this is confidential.
You don't know 是不对的。意思是你不知道。