MEQ’s or milliequivalents are a measure of a substance that incorporates the valance charge of that substance (Ca++, K+,Cl-) in addition to the molecular weight of the substance. There are equations that you can use to make this conversion if you know the valance charge of the substance and its atomic weight in moles. The proper conversion equation is:
mEq = mg/(atomic weight or molecular weight) × valence = mmol × valence
mg = mEq × (atomic weight or molecular weight) /valence = mmol × formula wt
Without knowing what substance you are referring to I cannot do this calculation for you because one would need to know the valence and the atomic of the substance to do the conversion.
There are many internet charts that can provide you this information or a local pharmacy should also be able to help you.