Trying to convert AAC files to WAV using iTunes, but I see no button for "convert using" in "edit preferences".
Am I looking in the wrong place?
iTunes will only offer to Convert any file not in the currently chosen file type in Prefs > General > Import Settings...
Menu offset for legibility
Whatever is set here will be the only available choice when you go to File menu > Convert >
...so the trick is to change your Import Settings to the output type you require.
The prefs are the same for Mac & Windows, only the appearance is different.