We shouldn't make noise here.(改成肯定陈述句)可以说一下规律或过程.He doesn't know how to get to the cinema.(改为同义句)改完后意思可以不通顺！改完后意思可以不通顺！改完后意思可以不通顺！

We should keep quite here.
He doesn't know the way to the cinema.

We must keep silent here.我们在这里应该保持安静。

We shouldn't make noise here.(改成肯定陈述句)
We should keep quiet here.
肯否定变化规律：
先找到句子的谓语动词,含有情态动词、助动词、be动词时,可用该动词形式的合适形式；不含有时,需根据谓语动词判断出所需要的情态动词、助动词、be动词形式,然后变化.例如：
Tom 【works hard单三式谓语,表明助动词用does】 at his lessons.变为否定句
——Tom 【doesn't 】work hard at his lessons.
这里原句中有【shouldn't make 】,表明要用情态动词【should】.
He doesn't know how to get to the cinema.(改为同义句)
He doesn't know how he can get to the cinema.
or
He doesn't know the way to the cinema.

we should keep quiet here
he doesn't know the way to the cinema.