You are correct that the plural marker is optional and jaghDaj can be interpreted as plural even without it. Sometimes the pluralness of the subject and object is specific in the prefix and limits it, but the null prefix does not prevent this particular combination. Thus you were correct when you offered the translation of "Worf kills his enemies" as a possible translation.
I'm thinking its jaghpu'Daj
That is correct.
if theres an official order?
Plural suffixes such as -pu' are type-2 noun suffixes while possessive suffixes such as -Daj are type-4 noun suffixes. 2 comes before 4 so it has to be -pu'Daj not -Dajpu'.
We don't teach the numbers explicitly but after a while, one order will start to "sound right" after having heard it several times.