What is the area of the sector ?

They forget to say "not to scale".  I'm guessing this is trig because I don't see another way to do it.

Let's consider x=chord PQ first.  By the Law of Cosines

We have an isosceles triangle formed by two radii of 9 cm and x=PQ.  By the Law of Cosines again,

The area of the circle is the fraction given by the angle,

24.7 sq cm

convert the answer to millimeters there are 25.4 millimeters in an inch and 12 inches in a foot so just divide the 5280 feet into a fraction of the numbers till you get to the simplest form you need so (5280 x 12=63360 inches) (63360 x 25.4=1609344 millimeters) (5280/12=440 feet) its as simple as that just break it down to it's simplest form.