I have no idea what he’s talking about.
我完全不知道他在说什么。
She has no idea how much I admire her.
她完全不知道我有多钦佩她。
We have no idea where the keys are.
我们完全不知道钥匙在哪儿。
Do you have any idea why the meeting was canceled?
你知道会议为什么被取消了吗？（注意：此句虽用 any idea，但含义相近）
They had no idea it would rain today.
他们完全没想到今天会下雨。
I have no idea how to fix this computer.
我完全不知道怎么修这台电脑。
He has no idea that I saw him yesterday.
他完全不知道我昨天见到他了。