The result will be in those cubic units. All inputs must be in the same units. This is half its diameter.
You can find the elliptic cylinder volume formula by knowing the semi-major axis minor axis and its height.
Area of the base pir2 if it was a circle half of that for a half circle. So A 12pir2. Use the formula for the volume of a cylinder as shown below. The result of the cos-1 function in the formula is in radians.