Important question: are you new in this? if you ask such question then I assume you are.
First you should do some research about trading and whole cryptocurrency industry. It's more complicated then you might think. Check some subreddits, especially r/BitcoinBeginners, they should be useful for you.
If you are referring to PLNCoin then according to CoinMarketCap, it's only tradable on YoBit which is an exchange that I wouldn't suggest for anyone.
I assume that OP is referring to PLN, a Polish national currency. and that's probably why people are writing about CoinDeal or BitBay here, cause this fiat is available on this exchanges