CCs (cubic centimetres) and mL (millilitres) are both volume units that have the same value but are derived from distinct base units. A volume expressed in CCs can be translated to mL by multiplying by 1, as 1 CC equals 1 mL.
The centimetre is exactly 1 percent of a metre and is derived from the metre. A cubic centimetre represents precisely 0.0001% of a cubic metre. The millilitre is derived from the litre, which, unlike the metre, is a volume unit. A millilitre is exactly 0.001% of a litre. Before converting a given volume of liquid measured with a ruler to litres or millilitres, it is most practical to determine the volume in cubic centimetres or cubic metres.