어떤 것을 고르는지 모르겠어요 어떤 - which (deciding between one or the other) 것 - thing 고르는지(고르다) - choose 모르겠어요 - I don't know

There is a subtle point about this phrase. The correct way to say "I don't know what to choose" is 어떤 것을 고를 지 모르겠어요. "... to (choose)" usually translates to "-ㄹ지". -ㄴ지 corresponds to present and present progressive tense conjugation, distinct from -ㄹ지. It is a small but important difference that changes the meaning. See these examples. I don't know what to do. 나는 어떻게 (무엇을) 해야 할지 모르겠다. (-ㄹ지 = to...) I don't know what I'm doing. 나는 무엇을 하고 있는지 모르겠다. (-ㄴ지 = present progressive) Is there anything he has to do? 그가 해야 할 일이 있어요? Is there anything he is doing / he does? 그가 하는 일이 있어요?

I'm not korean, so i think maybe it's 어느 것을 고르는지 몰라요.