Answer :

Hey there! Every 10 millimeters (mm) is equal to 1 centimeter (cm), so we can simply divide each of these numbers by 10 to find the answers.
2 cm, 6 cm, 30 cm, and 67 cm.
[tex]cm-centimeter\\mm-milimeter\\\\1cm=10mm\to1mm=0.1cm\\-----------------------\\20mm=20\cdot0.1cm=\boxed{2cm}\\60mm=60\cdot0.1cm=\boxed{6cm}\\300mm=300\cdot0.1cm=\boxed{30cm}\\670mm=670\cdot0.1cm=\boxed{67cm}[/tex]