Actually, Belthazar, for missions you don't need or want to make a jünk.
To create a new cargo type for a mission, you will need to add new entries to STR#s 4000, 4001, and 4002. This can be done either by copying those STR#s into your plug and editing them (simple, but not recommended), or by creating 'STR ' resources to "patch" the STR#s, as detailed in Appendix III of the Nova Bible (not simple, but recommended). If you choose the latter route, I think that the STR s that you will want will be as follows:
ID:9080 - Data:"*Some Guy" - I'm not certain about this one, as its ID isn't mentioned in either the Bible or Guy's RID Guide. It is the basic, fully-capitalized name of the cargo.
ID:9180 - Data:"*Some Guy" - This is the "lowercase" name for the cargo, but as the cargo is a proper name...
ID:9280 - Data:"Guy" - This is the abbreviation of the cargo's name, to be shown in the sidebar.
In any case, the number you put in the "cargo" field of the mďsn resource is the index number of the cargo within the STR# resources. The lowest unused index, and the one that the above STR s are patching, is 80.
Edwards