Poland and Sweden use power outlet types "C", "E", and "F", all of which can be connected using the adapter plug type "C" provided.
However, these EU countries standard voltage is 230 volts at 50 hertz, while the USA standard voltage is 115 volts at 60 hertz.
The adapter is not a transformer that changes the voltage and frequency, so your device must be capable of handling the 230 volts.
Fortunately, most devices, such as computer power supplies and phone charging devices, do handle both voltages. Check your device to be sure.