If i'm given the applied force of an object, normal force and acceleration how do i find mass

Force = (mass) x (acceleration)

Mass = (force) / (acceleration)

The mass of the object is . . .

       (force in the direction of acceleration) / (acceleration in that direction) .

If the normal force isn't in the direction of motion, then it isn't involved in the acceleration, and it can be ignored. 

(In more-complicated problems, the normal force might produce a friction force
along the direction of motion, and that would get involved with the applied force.)