$$\\85000000\;mm^3=85000000\;mm*mm*mm\\
\boxed{1dm = 100mm}\\
85000000\;mm*mm*mm*\dfrac{1\;dm}{100\;mm}*\dfrac{1\;dm}{100\;mm}*\dfrac{1\;dm}{100\;mm}\\$$
$$\\=\dfrac{85000000\;*dm*dm*dm}{100*100*100}\\\\
=\dfrac{85*100*100*100\;*dm*dm*dm}{100*100*100}\\\\
=85\;*dm*dm*dm\\\\
=85\;dm^3$$