Roll Roll Roll the sphere gently on the plank!

A solid sphere of mass $2$ kg and radius $0.1$ m is placed on plank with rough surface and of equal mass. But the plank lie on a smooth horizontal surface. The sphere is now given a sharp impulse in horizontal direction so that it starts sliding with a speed $18 \frac{m}{s}$ . After some time the sphere starts pure rolling on the plank. Given that the coefficient of friction between plank and sphere is $0.5$ . Now your task is just to find what is the time taken by sphere to start Pure rolling on the Plank in milliseconds . And take acceleration due to gravity, g = $10 \frac{m}{s^2}$ .