To find the volume of a right cone, we use the formula:
\[ V = \frac{1}{3} \pi r^2 h \]
where:
- \( r \) is the radius of the base,
- \( h \) is the height of the cone.
Given that the diameter of the base is 14 millimeters, we can find the radius:
\[ r = \frac{\text{diameter}}{2} = \frac{14}{2} = 7 \text{ mm} \]
The height \( h \) of the cone is given as 12 millimeters.
Now, we can substitute \( r \), \( h \), and \( \pi \) (given as 3.14) into the volume formula:
\[ V = \frac{1}{3} \times 3.14 \times (7)^2 \times 12 \]
Calculating \( r^2 \):
\[ (7)^2 = 49 \]
Now substituting this into the volume formula:
\[ V = \frac{1}{3} \times 3.14 \times 49 \times 12 \]
Calculating \( 49 \times 12 \):
\[ 49 \times 12 = 588 \]
Now substituting this back into the volume calculation:
\[ V = \frac{1}{3} \times 3.14 \times 588 \]
Calculating \( 3.14 \times 588 \):
\[ 3.14 \times 588 = 1847.92 \]
Now dividing by 3:
\[ V = \frac{1847.92}{3} \approx 615.9733333 \]
Rounding to the nearest hundredth:
\[ V \approx 615.97 \]
Therefore, the volume of the cone is approximately:
\[ \boxed{615.97} \text{ cubic millimeters} \]