Thanks, all! Yup, I'd done a quick check on the web but found references to types and names of adapter plugs with lots of data that only served to muddle my almost-packed-and-ready-to-go brain.
We've had these plugs (for France, etc.) in such abundance and for so long that I wouldn't begin to know their type. And, yes, I was pretty sure (from the web references) that it was not the UK plug. But one site was a UK site that talked about/compared their plugs to what was needed in Croatia so that added to my momentary befuddlement.
I forgot to mention that we will be in France for a couple of weeks before heading to Croatia so I should be able to do a bit more research in (say) a FNAC store. But it does sound like our mainstay plugs may be the right type. (This is for charging our phones, computer, camera batteries -- nothing fancy or high-draw (e.g., no hair dryers, etc.!!) Thanks again with all the quick and helpful responses.