To solve the problem it is necessary to apply the concept of Load on capacitors. The charge Q on the plates is proportional to the potential difference V across the two plates.
It can be mathematically defined as:
Q= CV
Where,
C = Capacitance
V = Voltage
Our values are given as,

Substituting values in the above formula, we get

Where

Therefore the charge must be 18pC to create a 30V Poential difference.