The 9-sided polygon will have a central angle between the vertex and the center of one side of 360°/(2*9) = 20°. Then the apothem is
a = (6 in/2)*cot(20°) ≈ 8.242432 in
The perimeter is 9*6 in = 54 in, so the area is
A = (1/2)Pa = (1/2)*(54 in)*(8.242432 in) ≈ 222.5 in²