\begin{align*}
5.26 \ \text{slug/ft}^3 & =\left( \frac{5.26 \ \text{slug}}{\text{ft}^3} \right)\left( \frac{1 \ \text{ft}}{0.3048\ \text{m}} \right)^3\left( \frac{14.59\ \text{kg}}{1\ \text{slug}} \right)\\
& = 2710\ \text{kg/m}^3\\
& = 2.71\times 10^3 \ \text{kg/m}^3\\
& = 2.71\ \text{Mg/m}^3
\end{align*}