Is there a way to add different mods to my server?

i´ve been playing a lot pixelmon reforged lately, but it was pretty hard to set it up localy, and when i found this site i was pretty happy, but a been wanting to put other mods that i used to have in my local world, like a backpack mod and some pixelmon sidemods. Is there a way to add some pixelmon sidemods like the gameshark or pokestops to my server and some other unrelated mods like backpacks? Thanks for your attention.

i see, but the backpacks mod is already in, the thing is that i haven´t been able to run the server with both the backpacks mod and the pixelmon modpack, is just one or the other, so before asking for it i want to ask if it is posible to run the server with diferent mods and modpacks

Thanks