Answer
(a) $Gg/m$
(b) $kN/s$
(c) $mm*kg$
Work Step by Step
We are given a pairs of units and asked to convert them to more appropriate SI units
a) $Mg/mm * \frac{1Gg}{1000Mg}*\frac{1000mm}{1m}=Gg/m $
b) $mN/\mu s*\frac{10^6\mu s}{s}*\frac{1N}{1000mN}*\frac{1kN}{1000N} = kN/s$
c) $\mu m *Mg*\frac{1m}{10^6\mu m}*\frac{1000mm}{1m}*\frac{10^6g}{1Mg}*\frac{1kg}{1000g}=mm*kg$