What is the correct way to pluralize an acronym?
Let's say we're talking about PLCs (programmable logic controllers)? Or are they "PLC's"? I've seen it both ways!
Either way is acceptable - it's a style issue. And by the way, your example isn't an acronym, it's an initialism or abbreviation. Acronyms are read out as words, like NASA, but not PLC or CIA.