For the first, I'm with you  the proper SI units are meters and newtons, not millimeters and newtons. For the second, remember that the power of 2 applies to both the M and N in MN. Hence 1 MN^2 = 10^6 x 10^6 N^2 = 10^12 N^2. Hence 4 x 10^10 N^2 = 0.04 MN^2. As another example of how this works, consider a square of size 1 KM^2. One square kilometer is not eqal to 1000 square meters, but rather is 1000m x 1000m = 10^6 m^2.
