So basically all you have to do is find the area of one of the smaller semi circles by using the formula for the area of a circle (A=πr^2). You know that the length of the larger semi circle's radius is equivalent to 6 cm because the radius of the smaller ones are 3 cm, meaning the diameter would have to be 6 cm and in this case, the length of the smaller semi circles' diameters is equal to the radius of the big semi circle. Then you would find the area of the big semi circle again by using the area of a circle formula, but after getting the answer you would half it, obviously because it's a semi circle. Subtract the are of the smaller semi circle you found earlier from the answer you just got and that's it ;) (you wouldn't have to half the area since there are two smaller semi circles and 1/2 + 1/2 = 1 but u knew that)
Put simply, the answer would be about 88.2644 cm because circles.