A conductor AB of length $l$ carrying a current i is placed perpendicular to a long straight conductor XY carrying a current I, as shown, the force on AB will act

The direction of magnetic field at any point on the wire AB will be into the plane of paper.

As we know the direction of magnetic field and also the direction of current, We can conclude that the direction of force acting on the current carrying wire will be parallel to the direction of X to Y.