See the attached graphic to see this solved for "r".
You should be very careful about stating the units for each of those variables.
time in seconds
radius in meters
mass in kilograms
G = 6.674 x 10^-11 m^3 / (kilograms * seconds²)
Also, it would be worth your while to go to this web page http://www.1728.org/kepler3a.htm
It has a calculator and other information about Kepler's Third Law.
Answer:
<h2>8</h2>
Step-by-step explanation:

Cool! So OK I'll take you through it.
You just need to take everything 1 step at a time, as you might already know.
First
3 to the second is 9
Second
The first part included like this 9*(3 to the third) which is 243
Third
The second part is included into the question like 243*(3 to the fourth) which is 243*81
Fourth
243*81 = 19,683
Your Answer
(3^2)*(3^3)*3^4) = 19,693
Hope That Helps and Correct Me If I'm Wrong!