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.
Converting Gallons and Liters. As stated above, one US gallon consists of about 3.785 liters. It means that to convert metric liters to US liquid gallons, you should multiply liters by 0,264. If you want to know how many liters are in some number of gallons, you need to multiply gallons by 3.785. The table below will help you to convert gallons and liters to other units of volume.