If the diameter is 3 feet, then the radius is 1.5 feet. Area of a circle = pi * radius squared or 
A = pi * (1.5)²
A = pi * 2.25
A = 3.14 * 2.25
A = 7.065 ≈ 7.1
7.1 feet² is your answer.
A = pi * (1.5)²
A = pi * 2.25
A = 3.14 * 2.25
A = 7.065 ≈ 7.1
7.1 feet² is your answer.