Iron comes from Iron Ore via the Forge. Iron Ore can be found in Iron Nodes in the Stalactite layer and Lava layer. The ore has to be harvested with an Extractor, as the node itself cannot be pulled with Power Cells, it also cannot be placed. All Ores can be smelted into bars in a Forge for further processing.
It depends on the substance (water for example has 1000 grams to a liter, other substances have more grams or less grams to a liter depending on a property (called the density measured in grams / liter) of the substance.
1 kilogram/cubic meter is equal to 0.001 kilograms/liter, or 0.00208635112182 pound/quart. Note that rounding errors may occur, so always check the results. Use this page to learn how to convert between kilograms/liter and pounds/quart. Type in your own numbers in the form to convert the units!