There's no noun suffix that works like the verb suffix -qu' to emphasize or highlight whatever immediately precedes it. That is, there are no rovers for nouns. The placement is fixed. Dujmeyna' means "definitely ships" or "undoubtedly ships." It doesn't necessarily mean "a number of ships and not just one" even though -na' follows -mey.
It turns out it's a little more complicated or subtle, however.
The word jaghpu'na' could mean "definitely enemies" (that is, there's no question that those people you're talking about are enemies and not friends or neutral parties or whatever), but, in the proper context, it could also mean "definitely (several or a lot of) enemies," focusing on the group or plurality.
Going back to Duj, the context might be:
Speaker #1: Duj Dalegh'a'?
Speaker #2: Dujmeyna' vIlegh.
"Do you see a ship/ships?" (In English, one has to indicate singular or plural; in Klingon, of course, it's ambiguous or unstated.)
"I see what is unquestionably a bunch of ships." (-mey makes the plurality explicit, but -na' emphasizes the plurality: There's no doubt that there's not just one ship out there!)
For the possessive suffixes, however, this doesn't work. jaghna'lI' means "definitely your enemy (and not your friend, etc.)." It doesn't specifically mean "definitely your enemy (and not mine)."
If you want to emphasize the possessor, just give it extra stress when saying the word: DujlIj (or DujlIj or DujlIj or DujlIj or DujLIJ or however you want to transcribe it).