The autogen is held in the dsf files contained in ...X-Plane/Global Scenery folder.
The orthophoto tiles do not contain the autogen, because most of the time, when you have enough space and power to use orthophoto tiles, you want a more dense overlay than the one provided by default. Very often, you will want something from Simheaven, made with W2XP, which is baked from more recent OSM (Open Street Map) data.
If you still want the default autogen, you can extract it with Ortho4XP and place the resulting overlay above your orthophoto tile, in ...X-Plane/Custom Scenery folder.
You will find more information about that in Ortho4XP manual, on X-Plane.org forum, on YouTube or even just on Google. This forum is mainly intended for X-Plane default install.