Question

I had no idea where to spend the night. ( rewrite as a an affirmative sentence)

Answer 1

I have an idea where to spend the night

Answer 2

I had no idea where to spend the night. => I was in the dark about the idea where to spend the night.
Or
=> I was ignorant of the idea where to spend the night.
Or
=> I was unconscious of the idea where to spend the night.