I stood there blankly, not knowing what to do.

我茫然地站在那里，不知道该怎么办。

youdao

There he sat in great grief and fear, not knowing what to do.

他坐在那里，又伤心，又害怕，不知道怎么办才好。

youdao

Many people graduate from school or college not knowing what to do with their lives and get a job without really thinking about it.

许多人从中学或大学毕业时，不知道他们的人生该做些什么，没有真正思考就找了一份工作。

youdao

Finally, one of them made a remark about people not knowing what to do with their lives.

NEWYORKER: Silence, Exile, Punning

Adults can be discouraged from exercising by not knowing what to do or how to do it.

WSJ: Hard-Wired to Hate Exercise?

The rest of the party was awkward and I left with a bad feeling, not knowing what to do.

FORBES: Getting Past A Communication Impasse