The question is open to multiple interpretations but I think you mean
[(-2m)^4] x (n^6)^2 = [(-2)^4](m^4)(n^12) = 16(m^4)(n^12)
or 16 times m to the 4th power times n to the 12th power.
The number is 400
1.39 times 10 to the 2nd power is 139
400
4C2 * (-2CD2) = -8C3D2
43 times 32 = 576
729
120
790
8,730
800
114
279