Where's the Web Services Tab??

Hi there--I'm putting together a survey for use on Amazon's mTurk platform. When the responder completes the survey, I need to generate a confirmation code they can enter and get paid. I've been following the steps outlined in this tutorial https://blog.mturk.com/tutorial-getting-great-survey-results-from-mturk-and-qualtrics-f5366f0bd880. Unfortunately, when I click on survey flow and add a new element, "web services" is not there, and I need that to point to the qualtrics random number generator. I've looked through the documentation on the qualtrics site but it also situates web services in the survey flow block. The "end of survey" block allows one to set a custom message, but no way to call the rannum generator. Please advise! Thanks! !