There are a number of ways to express concentration of a solution. This includes molarity. It is expressed as the number of moles of solute per volume of the solution. For example, we are given a solution of 2M NaOH this describes a solution that has 2 moles of NaOH per 1 L volume of the solution.
0.150 M NaCl = 0.150 mol NaCl / L solution
mass of NaCl needed = 0.150 mol NaCl / L solution ( .100 L ) (58.44 g/mol) = 87.66 g NaCl needed
Hope this answers the question. Have a nice day.