The question, as stated, cannot be answered sensibly. A millilitre is a measure of volume, with dimensions [L3]. A pound is a measure of mass, with dimensions [M]. The two measure different things and basic dimensional analysis teaches that you cannot convert between measures with different dimensions such as these without additional information.
As a simple mental exercise consider a millilitre of air and of water. They will have very different masses.
400 US gallons = 51,200 ounces.
400
400 fluid ounces is 3.125 US gallons or 2.602 Imperial gallons.
400 cubic meters = 87987.7 Imperial gallons
25 gallons.
400
There are 400 gallons. 4 quarts = 1 gallon. So 1600 divided by 4 = 400
100 gallons
If by inches, 409 gallons. Probably 400.
3000
1600 liters is equivalent to approximately 422 gallons.
3.125 gallons is 400 fluid ounces. (US)