this sounds like a standard thermodynamics equation.
assuming this is a close system,
dU = Q + W
Q = -65.4J (heat given out to surroundings)
W = p.dV
although you are right to use p.dV = 0.965(0.335), the answer you get is not in Joules. In order to get joules, you must convert p to Pascal and dV to m3