At point P, Maxwell cork skew rule defines the direction of magnetic field and Fleming's left hand rule reveal the concept of force on the charge in this field.

According to Maxwell's cork screw rule the direction of magnetic field at point P in plane of paper is perpendicular to the plane of paper inwards i.e., along z-direction.

Now since charge is moving along x-direction therefore, from Fleming's left hand rule stretching the fore finger in direction of paper inwards the thumb will indicate the direction of force F acting on the charged particle along oy.