A CONDUCTING CIRCULAR LOOP OF RADIUS O.25M IS PLACED IN THE XY PLANE IN A URNIFORM MAGNETIC FIELD OF OF 0.360T THAT POINTS IN THE POSITIVE Z-DIRECTION THE SAME DIRECTION AS THE NORMAL TO THE PLANE. CALCULATE THE MAGNETIC FLUX THROUGH THE LOOP

this should help:

physics.stackexchange.com/questions/225145/how-to-calculate-the-magnetic-flux-through-a-circular-area