Phyton script with blender

Hello! I was wondering if you would be able to help me or give some advice on how to proceed. I have 3D files of Tokyo city, split into hundreds of small squares like the files attached. I want to be able to 3D print scale models of specific sections of the city. So, the steps would be something like: 1. Combine all the squares into one big file 2. Find the lowest point on the model (likely sea level), then add a small base a bit lower than that across the whole area. 3. Select an area to print, isolate that section 4. Apply a grid to cut it up into printable squares. The size of the squares will depend on the scale of printing, so it's not fixed. I think the mesh files are fairly good, without serious holes etc. But everything has zero thickness so they need to be processed a bit to be 3D-printable. Please let me know if you know a good way to achieve this or if you have further questions. Thanks!