What do you do if you get a number that is not on the Normal Distribution table as it is too high so above 3?

Suspect you've made a mistake in your calculations.

Looking at the Normal curve, the area under it between the mean and 3.09 standard deviations is [approx] 0.4990, ie the probability that the data could exceed 3.09 standard deviations from the mean is 2 x (0.5-0.4990) = 0.002 = 0.2% [using a half-tail table], ie it is quite unlikely that a data point is much further away from the mean than the tables' limit of 3.09.

Beyond 3[.09] standard deviations away from the mean, the area under the curve changes very little in the first 4 dp, so [most] tables are going to not be of much help anyway - when 4 standard deviations away are reached, it is almost all the distribution and rounds to 1.

So if you are looking at a point greater than 3 standard deviations away from the mean it is either a very unusual event that has caused it, or (more likely) you've made a mistake in your calculations.