Magnetic energy of solar flare

The problem reads as:
"The magnetic field permeating a region of space represents stored energy.  This energy is often quantified in terms of its density (magnetic energy per unit volume) given by  B^2/(2*u) where u=4*pi X 10^(-7).  Suppose an "X2" flare occurs within a volume of 10^12 km3 over a sunspot pair initially permeated by an average magnetic field strength of 1000 Gauss.  Calculate the total magnetic energy in Joules stored in the volume before the flare occurs. "

My dilemma.....I know that the given formula for magnetic pressure is a simplified version of the entire magnetic momentum flux relationship.  But how can I use what is given? (a relationship in terms of density seems to continually yield a result of Newtons/meter2 which I understand to be magnetic pressure?  I have resorted to blindly "plugging and chugging" in a an effort simply to get the right units.  I assume that I should be able to take 1000 gauss over the given volume with the given mag pressure relationship and somehow attain an initial energy.

Thanks for any insight you might provide.