The apostrophe and 's' were used to pluralify Iraqi

Pluralize. Your "POW" example is a good one. Not all people documenting rules of English recognize it, and I was taught both ways. Notably, pluralizing an acronym or a referenced item (typically a letter or a symbol) allows use of an apostrophe. The POW example you cited is an example of the former, and not a required use of an apostrophe in all sources. An example of the latter would be:

We dotted the i's, but still need to cross the t's on the new contract.

I'm not familiar with any sources which do not require this use for an apostrophe, but I may be painfully unaware. Note also:
GOOD
1990s
'70s (contraction of 1970s)

BAD
1990's
70's (unless it's a business named 1990, or something with a "handle" of 70, or such)

So this can be generalized as:
-Do not use apostrophes when pluralizing.
-Do use apostrophes when indicating any singular possessive. (My parent's car, if I had only one parent)
-Do use an apostrophe when indicating a plural possessive, but do not add a trailing s if the word already has an s for pluralization. (My parents' house, if I have more than one parent; The children's room.)

Expect ridicule if you open a restaurant and call it "Food's Express", unless your name is John Food.