The template doesn't use Autotile, it uses External Tilemap object for the level making.
But you can easily replace the tilemap object with sprite object and use my Autotile extension to do the job π
https://vegetato.itch.io/autotile-extension
or if you want to go with internal Tilemap object, and wants autotile, then i suggest you take a look at my Farming Template
https://vegetato.itch.io/farming-template
I built an autotile system in it that uses gdevelop Tilemap object (not an extension though, but soon will turn it into an extension), you can use the same system in any of your projects (Copy-Paste the group event) :)