Is 1 militer equal to 10 milligrams?

Answer 1

No.

First of all, there is no such word as a militre so I am assuming that you meant millilitre. However, in that case there can be no comparison because a millilitre is a measure of volume while a milligram is a measure of mass. The two measure different things and, according to basic principles of dimensional analysis, conversion from one to the other is not valid.

The masses of equal volumes of the two substances will clearly be very different. So there is no direct conversion between mass and volume: you need to know the density of the substance to enable you to carry out the conversion.

Answer 2

No, a milliliter (mL) measures volume, while a milligram (mg) measures mass. The conversion between the two depends on the density of the substance being measured.