Select meshes by normals orientation

Hi, I need to select all meshes with normals facing one direction in Rhino (yellow in the image) to flip them. image
I figured that there is no default way except for writing a script. I don’t work in Python and never used scripts for Rhino before. Could you lease assist on how I could solve this with detailed guidelines?
Thank you

Just join the mesh and use UnifyMeshNormals command

I’ve tried that. But it doesn’t get it right image

Would be helpful if you would attach your file

here it is. It is quite large. Thank you for helping!

There is no file attached, also how large can it be it is just a mesh box, just attach a file containing the mesh box in your screenshot.

It was just one isolated element because it’s hard to do manipulations with the whole file. Here is the link https://www.dropbox.com/s/p1yoh718q0gdrya/CBD.3dm?dl=0

select that mesh. Go to file > Export Selected > Export it as a Rhino file. Upload that Rhino file here. We don’t need this 300+MB rhino file.

Example.3dm (17.6 MB) Here is one building from the model as an example

pretty messy… first use SelCrv then hide or delete them. use SelDup and delete. now join, it will tell you that the mesh is disjoint. use MatchMeshEdge on the resulting mesh with a value of 0.1 for example. now use UnifyMeshNormals.

It worked. Thank you so much!