Answer is 18.84 cm
Step by step:
C= 2 TT r
C = 2 pi radius is the formula.
You didn’t indicate if 3cm is radius or diameter so I did both
If 3cm is radius
C= (2) (3.14) (3) = 18.84
If 3cm is diameter, you will find radius is
1/2 diameter. 1/2 of 3 = 1.5cm
C= (2) (3.14) (1.5) = 9.42cm