10000 milligrams=

1000 milligram = 1 gram
$$\begin{gathered} \Rightarrow 1\mathrm{mg}=\frac{1}{1000}\mathrm{g} \\ \Rightarrow 10000\mathrm{mg}=\frac{1}{1000}\times 10000=10\mathrm{g} \\ \mathrm{Also};1000\mathrm{g}=1\mathrm{kg} \\ \Rightarrow 1\mathrm{g}=\frac{1}{1000}\mathrm{kg} \\ \Rightarrow 10\mathrm{g}=\frac{1}{1000}\times 10=\frac{1}{100}=0.01\mathrm{kg} \\ \mathrm{therefore};10000\mathrm{mg}=10\mathrm{g}=0.01\mathrm{kg} \end{gathered}$$