To find the volume of a sphere, you can use the formula:
\[ V = \frac{4}{3} \pi r^3 \]
where \( r \) is the radius of the sphere.
Given that the diameter is 12 m, we can find the radius by dividing the diameter by 2:
\[ r = \frac{12}{2} = 6 , \text{m} \]
Now, substitute the radius into the volume formula:
\[ V = \frac{4}{3} \pi (6)^3 \]
Calculating \( 6^3 \):
\[ 6^3 = 216 \]
Now substituting that back into the volume formula:
\[ V = \frac{4}{3} \pi (216) \]
\[ V = \frac{864}{3} \pi \]
\[ V = 288 \pi , \text{m}^3 \]
Therefore, the volume of the sphere is
\[ \boxed{288\pi} \text{ m}^3. \]