The ribbon length around the dish can also be labeled the circumference. The equation for circumference is C= ∏d or Circumference is equal to pi x diameter.
You can use 3.14 as pi and the diameter is 3 inches so your equation would read Circumference = 3.14 x 3
Circumference= 9.42 inches
So the ribbon would need to be 9.42 inches to wrap around the pie dish.