The units in order are millimetres, centimetres (10 times as big as millimetres) and metres (100 times as big as centimetres), but to compare the measurements we need to get them all into the same units. Let's pick centimetres, because they're the middle units. So we have 142 cms, 137 cms, 139.7 cms. Now it's easy to compare them: 137, 139.7, 142: 1.37m, 1,397mm, 142cm.