To what probabilities do each of the following sigma levels correspond, based on a standard normal curve: 3 sigma, 4 sigma, 5 sigma, and 6 sigma?

Check figures: for three sigma, the two-tailed probability equals 0.27%; for six sigma, the two-tailed probability level is 0.0000002%. To what level of defects per million do each of the two-tailed probabilities correspond to? What is the point of these calculations?