Please share how it goes! Some drills have the measurements, but it all comes down to players level and age. If the team is more advanced, using this drill with a smaller triangle would be beneficial!
For this drill? From experience, I have used a triangle of 10 yards. Gives the players enough space to move, but also encourages a quick sprint between the cones so the players keep up the pace!
The players on the outside rotate by going from top to bottom and the back (bottom to top). Though you can change the rotation and even have them rotate through the triangle!