coil having 1000 turns and a length of 3.14cm carries a current of 5A. calculate the magnetomotive force and the magnetizing force

If the "length" of the coil is its circumference, the coil radius is

a = 0.5 cm = 0.005 m

If you want the value of H at the center of the coil, it is

H = N*I/(2 a)

and B is mu-o times that.
N is the number of urns.