Your solution contains 0.32 g of sodium chloride.
So, you know that your sample weighs 16 g and that it's 2% m/m sodium chloride. You can use this data to determine how many grams of sodium chloride must be present in that much solution by
Think of it like this: you know the mass of sodium chloride represents 2% by mass of a solution. To get from 2% to 100% you need to multiply by 50, so the mass of sodium chloride can be determined by dividing the total mass by 50.
For example, if you have a 25% m/m solution that has a total mass of 16 g, the mass of sodium chloride would be 4 g.
That happens because you need to divide 100% by 4 to get to 25%, so divide the total mass by 4 to get the mass of the solute.