Answer is
If 6cm is Radius, = 37.68
If 6m is Diameter, = 18.84
Formula
C = 2 pi r
C = circumference
pi = the constant pi 3.14
r = radius of the circle
Radius of 6
C= 2 x 3.14 x 6 = 37.68
Diameter of 6
Divide by 2 to get radius of 3
C = 2 x 3.14 x 3 = 18.84