FCK host the first-leg of their Champions League round 16 tie.
Elyounoussi said of his Norway teammate: "I know him well from the Norwegian national team, of course.
"There are also a few other players in City's squad that I have played with. For example, I know Akanji quite well. It will be good to see those guys again."
On how to stop Haaland, he added: "If I knew that, I would have made many millions from it.
"There are certainly many who would like to know.
"Everyone here has seen the Premier League and knows what he is good at, so we have to try to keep him away from the goal."