The formula for the circumference of a circle is 2 x Pi x R, or Pi x D.
Since we have our formula, we will need to divide.
When looking for the radius when given the circumference/area, it is important to cross out what you've divided by so you don't accidentally get confused.
Divide 120 by 3.14 and then cross out Pi from the formula, leaving us with 2 x R.
120 / 3.14 = 38.21
Divide 38.21 by 2 and then cross out 2 from the formula, giving us R.
38.21 / 2 = 19.1
Your radius is 19.1 meters.
I hope this helps!