How to find volume of substance from molar concentration
Nothing has been said about the actual volume of the solution, only concentration of the solution has been given.

Assume that $c$ moles of solute is present in 1m$^3$ of solution.

Then mass of solute=c*molar mass 

volume of solute * density of solute = c* molar mass

From this equation, volume of solute can be known.

Clearly, if the volume of the solution increases, the volume of the solute will also increase. Since the volume of the solution has not been given, it must give you a hint to take the above assumption.