This page shows you the formulas for the calculation of energy storage, electric charge, and potential difference. As per the energy storage formula, dividing the product of electric charge and the potential difference with number 2 will give the storage. And potential difference formula says that dividing the product of electric charge and the energy storage with number 2 will give you the result. But for the electric charge just divide the two times of energy storage by potential difference.
Use the above given electric charge formula to calculate the electric charge in coulomb unit. All the three formulas need only basic arithmetic operations to get the result.