Unless your Admin placed a user defined field into the test template on the Test Planning area, there is no Test Run # there by default. In this case you should ask your Administrator. In the pre-TD8.0 versions I believe there was a Test Run Number in the Test Lab, Grid view. I believe it was there to indicate the number of times a test was run during a test set execution.
By setting up the properties of a test set you could have tests repeat on failure, or on failure call another test.
Success is the ability to go from one failure to another with no loss of enthusiasm.
~ Winston Churchill ~