Need help with ground level please

Have an old world file that i'd like to make a copy of the base and use it on our current world. Problem i'm having is how to save the ground level, it's part dock so water is involved and different heights. Is anyone able to help guide me on how to set the floor so I can place it anywhere and the ground will adjust or possibly make a blueprint for me to use if someone out there has good skills :)

The base is just south of the starting ring along the road created.

World save download