A family of Microsoft word processing software products for creating web, email, and print documents.
Umm ... Go File -> Options -> Proofing -> AutoCorrect Options, and it's there, looking just like it always did.
Note that the original question is about losing the option (in Word 2016/365) on the right-click menu to create AutoCorrect entries which "fix" spelling errors. A similar option has now been restored in the new Editor (spelling and grammar check) right-click options in Word as part of Office 365.