Even though the above screenshot displays the required content for the unofficial Blacksmith server, it is exactly the same problem with the main official 506th server as well. I already have the Mod Pack 1.3 in my mod folder below:
I also loaded the addons too. Below is the list of all my mods:
I am also not sure where to get the Maps Pack 1.3 as that is not a listed download at the 506th Public Server thread. But I did get the Mod Pack 3.5.8 from that same thread yet its not showing in my addons above.