@uth6287b4 welcome to the forum.
I believe that the AI features have been added to the 3.7.x version of Joplin. You can see the features being mentioned / added in this post..
v3.7.x is currently only available as a pre-release with the full release due to be published in the first week of September.
I would guess that the documentation is currently also being updated along with the app.