what to do with it 、 how to deal with it 、how to do with it的

what to do with it:该怎么处理；how to deal with it:该如何解决；how to do woth it:如何处理.没听说过 what to deal with it 的用法.
如果某人给你一张纸,你问 what to do with it?就是问可以干嘛呢?写字 画画 折纸等的回答.而 how to do with it?是你知道对方给你是干嘛的,但是如何写 如何画 如何折 才是回答.
how to deal with it,一般用在解决问题上面.比如 桌子上多了一张纸 你问 how to deal with it.该如何处理?丢掉 拿来用 才是这个回答

I don't know what to do with it.=I don't know how to deal with it.
这两个是一个意思。 what 是do的宾语；how 是副词修饰deal.

how to do 是怎么干，有明确目的
what to do 是干什么，无明确目的