Hi, I need to create a surface that contains all the faces that form that wall shown in the picture. The assembly is made from different 3D parts and I need to create a single surface that contains all the part faces that are on the same wall's side.

There's obviously the possibility to manually select them one-by-one but it is very cumbersome since their number is huge.

Does someone know a method to quickly do what I need? Also using a script if necessary.

Thank you!