In this case the
mkmol stands for
micromole. The correct abbreviation should be
μmol but with some browsers there are problems with displaying symbol
μ.
Screening compounds are commonly ordered in micromoles. You can order compounds on a 96 well plate. If you choose 5 miromoles of each compound, for example, suppliers will weigh the appropriate amount of each compound depending on it's molecular weight. Then all you need is to add 500 microliters of DMSO to each well and you will have ready for testing samples of 10 mM solution.