The currency of Croatia is Kuna. You can easily exchange money at the offices located in the airport, railway stations, bus stations and ferry stations. Please note, these offices are not open 24*7, so it is advisable that you prepare days before you land Croatia. There are many reliable online options you can check. Also, you can exchange your money at a bank or an ATM.
However, you must know that the Croatian Kuna cannot be exchanged outside Croatia. You might as well decide to go for last minute shopping to finish off the currency or else get it exchanged back to your home currency at one of the banks there. Euros are widely accepted in Croatia as most of the facilities and items here are tagged in Euros. But this is unofficially done simply to please the many European tourists visiting Croatia every season. Accepting Euros save the travelers time and energy.