Number of $H^{+ ions}$ present in 500 ml of lemon juice of $P^{H}=3$ is

Question

$\begin{array}{1 1} (a)\;6.5 \times 10^{-12} \\(b)\;5.65 \times 10^{-23} \\ (c)\;3.01 \times 10^{20} \\ (d)\;1.506 \times 10^{-20} \end{array}$