Hey!
So, we know that the formula to find the volume of a cone is

The radius is half the diameter, so in this case our radius would be 2. Let's plug in the values.

Simplify.

The thing we are left with is just a multiplication problem. Let's simplify it. Let's remember to also input the units since we are talking about the volume of a figure.
V≈37.68 in³
Instead of using the equal sign (=), we had to use the approximation sign (≈) since we are using a rounded version of pi (

)
Thanks!
-TetraFish