Your package should have the option to plot BM contours as well as stress contours. If its steel plate it's probably more convenient to calculate the Von Mises Equivelant Stress and compare it to the yield stress (provided that the element is not susceptible to buckling. Wood-armer moments are also handy if its a slab, as it will calculate an equivelant moment which takes into account torsion.
Alternatively you could plot the appropriate stress with section depth to calc maximum Mx,My,Mz etc. The bending moment may then be calculated by integrating the compressive and tensile stresses and establishing the lever arm with them.