It's been removed. Probably they where fed up with it after 8 new versions of LabVIEW...
They did not remove it from the help, and that is a bug.
It's not just the menu that is missing. It used to be in "National Instruments\LabVIEW 2013\resource\Framework\Providers\Builds\AppBuilder\ConvertBuildScript", and there is nothing like that in 2017...
Guess you have either read in in Notepad (not sure how that will work) and convert it manually, or find a <2015 version (not sure how that will work either). For a lot of applications simply starting over will be the shortest path.