Solve C1V1 = C2V2 for stock volume, diluent, or final concentration, in common lab units.
C1V1 = C2V2 says the amount of solute you take from the stock equals the amount in the final solution. Rearranged, the volume of stock is V1 = C2V2 / C1, and the diluent is V2 − V1.
Molar units convert among themselves, and mg/mL, µg/mL and ng/µL convert among themselves. A mass concentration cannot be turned into a molarity here without a molecular weight.
What is the diluent volume? Final volume minus the stock volume you transfer. For 50 µL of a 1 in 10 dilution, that is 5 µL of stock and 45 µL of diluent.
Can I dilute from mg/mL into µM? Not in this calculator. Those units are different kinds of concentration. Convert one of them first, using the molecular weight, then come back.