An alternative way of calculating the molarity of the HCl solution is to use the fact that as a strong acid, all of the H+ and Cl- dissociate. The pH = -log10([H+]) and thus the concentration of HCl is given by [HCl] = 10^-pH. Using this relationship and the pH of the solution before any NaOH was added, calculate the molarity of the HCl solution.

I'm not really sure how to use this information and calculate the molarity

Question

An alternative way of calculating the molarity of the HCl solution is to use the fact that as a strong acid, all of the H+ and Cl- dissociate.  The pH = -log10([H+]) and thus the concentration of HCl is given by [HCl] = 10^-pH.  Using this relationship and the pH of the solution before any NaOH was added, calculate the molarity of the HCl solution.

I'm not really sure how to use this information and calculate the molarity