didn't know at all
무슨 말 인지 전혀 몰랐다.
I had no idea what they were talking about.
그들은 목숨을 구해 준 보답을 하고 싶어 했지만, 어떻게 해야 할지 전혀 몰랐다.
They wanted to repay the person who had saved their lives, but they had no idea how.