Question

He is sure of his facts. (change into an interrogative sentence)

Answer 1

Is he sure of his facts?

Answer 2

Hola

Here is your answer

Question - He is sure of his facts.

This sentence is affirmative

Interrogative - Is he sure of his facts?

Or , Isn't he sure of his facts ( this can be written if u convert affirmative to negative sentence if needed or told)

Hope it helps