Use the formula for energy stored between the plates of a capacitor:
[tex]E = \frac{1}{2}QU=\frac{1}{2}7.6\cdot 10^{-11}C\cdot 5.8V= 2.2\cdot 10^{-10}J[/tex]
where Q is he charge (given) and U is the electric potential (aka voltage), given.
The stored energy is 2.2 10^{-10} Joules.
