Well, no, because the terrain doesn't have a fixed set of vertices. It makes them up on the fly at runtime, using more for terrain that is closer and less for terrain that is far away. If you watch carefully you can see the detailed geometry change as you move around.
Sounds like you want to just convert your Unity terrain to a mesh. There are lots of tools out there for doing that. Search for "unity terrain to mesh" and have a fun afternoon.