From the motherboard site you linked to, under specifications it says it has 4 x DDR4 DIMM slots. Also says that the board supports up to 64GB of RAM, which would be up to 16GB per slot. As suggested above, you should look at the actual RAM stick to see the part number, or add up the individual chips on the stick.
I would suggest you should buy 2 8GB sticks as a kit (they will be tested together). That should be enough for most common uses, 8GB might be on the low side for some of the newer games.