The JoC-Missions-addon.zip file you have requested: Add Ons / JoC Missions Add-On - 3.4mb is not available. Perhaps try browsing all files for the game Silent Hunter IV: Wolves of the Pacific and upload any files you want to share or are missing. This is the only information we could locate:
An additional pack for the JoC-Missions-Pack. It consists of a few new missions to play as single mission. An add-on for the JoC-Missions Pack with new missions.