Set the fat and protein composition:
The composition determines milk density and therefore the conversion from weight to volume.

Set the composition measurement basis:
Fat and protein is measured as either % mass/volume (m/v) or % mass/mass (m/m). Typically if quantities are reported as volumes use m/v if reported as weights use m/m.

Set true or crude protein:
This affects the milk density (very slightly). True protein is used in Australia, US and France whilst crude protein is used in the most of Europe and New Zealand.

Enter the milk quantity and units:
Enter the quantity to be converted and select the units of measure from the list box.

<= And here you have the answer!
The equivalent quantity in common international units is calculated here.