What is needed to add a drive cage to a HPE ML350G9?

First i appologize if this is an inapropriate place to ask this.
Im new here.

I have a HPE ML350 G9 tower server which currently has an onboard P440AR controller and one drive cage that is filled with 8 SATA SSD’S.
Im trying to figure out how i can add another 8 bay drive cage to this server. Like what parts are required? do i need an additional raid controller? etc.
Im aware i definitely need a drive cage. But beyond that information is muddy.
And i just cant find anything. If anyoine here ios familiar and can help it would be greatly appreciated!