Here's a few tips for you if you cant see the arrows on the side of the fans.
For fans that you want to pull air in ..... get a small piece of paper about the size of a post it note and hold it against the pc casing and then let go of it , the fan should be strong enough to stop the paper dropping on the floor.
For fans you want to remove hot air repeat the above and if they are the right way round to get rid of hot air the paper should either drop on floor or if it is mounted on the roof of the case you should see the paper move because it is trying to blow it out of the way of the airflow.
I thought the guys who built my custom games rig had put the front fan the wrong way because when i put my hand against the fan i could feel a draught , they gave me the tip of putting a piece of paper against the fan , it did not drop on the floor so i knew it was the right way round.
In my coolermaster haf x tower i have 2 rear fans , a huge Noctua NH-D15S Ultra Quiet Performance CPU Cooler , a large side fan , a roof fan , a front fan and of course 2 fans on my gtx 1080.