Hey there!
Formula for the area of a circle:

Formula for the radius of a circle:

First, let's divide the diameter by 2 in order to find the radius.
16/2 = 8
Next, we'll plug our values into the formula (found above).
A = pi x 8^2
A = pi x 64
A = 64pi^2 or A = 201.1cm^2
Hope this helps!! :)