The area of a circle is defined as Pi R^2
Since we only have the diameter and Pi, we need to solve for the radius.
The radius is 1/2 of the diameter, so divide 6 by 2 to get our radius.
6 / 2 = 3
Our radius is 3.
Now let's plug in our formula.
A = 3.14 x 3^2
3 x 3 = 9
9 x 3.14 = 28.26
Your area is 28.26 units ^2
I hope this helps!