800 milligrams is a measure of mass and does not have any visible characteristic. The volume occupied by an object with a mass of 800 milligrams will depend on 800 mg of what substance.

There are a million (1,000,000) milligrams in a kilogram. Therefore you have to multiply by this factor. 90,000x1,000,000 is 90,000,000,000 milligrams.

You measure a Bicycles mass in KILOGRAMS. You would measure the weight of an APPLE in Grams, and the weight of your brain in milligrams, if you think you would meaure a bike in grams or milligrams.

You can say: "How many milligrams are in a cup of grapes?". Since a milligram is a unit of mass, you might also say: "What is the mass, in milligrams, of a cup of grapes?"

cc are a unit of volume, and milligrams are units of mass. They cannot be converted directly but if a particular substance say, pure water, is used, then since a cc of water has a mass of 1 g, then .5cc of pure water has a mass of 500 milligrams.

It could refer to density, where the mass is measured in milligrams and the volume in decilitres. Or It could refer to concentration in a fluid where the mass of the "active" substance is measured in milligrams and the volume of the solution (possibly solute) is measured in decilitres.

milligrams is a unit of mass and ml is unit of volume, you have to know the density of material to determine how many milligrams a ml of that material weighs

Milligrams is a unit of mass. Milliliters is a unit of volume. To convert between these units you must know the density of the substance. Density = mass / volume.