Answer
$131\ m^3$
Work Step by Step
The volume of the pyramid is given by
$$
Volume= \frac{1}{3} \times base \ area \times height= \frac{1}{3}\times \frac{1}{2} (6.71)(8.47)(13.8)=130.718\ m^3\approx 131~m^3
.$$
Where we used the fact that the base area is given by the area of a triangle:
$B=\frac{1}{2}\times base \times height$
