We know that the volume of the cone is:

V = (1/3) * area of the base (a) * height (h)

63 = (1/3)*a* 4

63= 4/3) *a

==> a= 63*(3/4) = 47.25 cm^2

But we know that the area is:

a= pi*r^2 (where r is the radius and pi=3.14)

==> 47.25= (3.14)*r^2

==> r^2 = 47.25/3.14= 15.05 (approx.)

==> r= sqrt(15.05) = 3.88 cm (approx.)