Since friction is acting at the lower most point P, angular momentum conservation can be applied about the lower most point.

Angular momentum initial

$L_i= MV_{cm}R+ Iw$

$\qquad = Iw$[since $v_{cm}=0$]

$\qquad= \large\frac{MR^2w}{2}$

Angular momentum final

$L_f= MV_{cm}R+Iw'$

$w'= \large\frac{V_{cm}}{R}$

$\therefore L_f= MV_{cm}R+\large\frac{MR^2}{2} \frac{V_{cm}}{R}$

$\qquad= \large\frac{3}{2}$$ MV_{cm}R$

$L_i=L_f$

$\large\frac{3}{2}$$MV_{cm}R= \large\frac{MR^2w}{2}$

$V_{cm}=\large\frac{Rw}{3}$