If AC Milan is in need of a number 9 this season, they should sign Rasmus Hojlund from Manchester United. There's a big chance that Rasmus Hojlund would perform well at AC Milan since he's Serie A proven. Manchester United wants to sell Rasmus Hojlund this season and they are yet to get a buyer as it stands now. If AC Milan approached Manchester United to sign Rasmus Hojlund this season, AC Milan would sign him easily because they would have no rival.
If Milan wants to get Hojlund from United, I think they need to compete with Napoli, who have already shown interest in the United striker. There are even rumors that they are close to reaching an agreement.
That hasn't happened yet, and I think Milan still has a chance if they have a more attractive offer to be considered by United and Hojlund. However, it may ultimately depend on Hojlund's interest in choosing his new club.