Turning model into fully textured mesh

Is there any way I can turn a model (made up of unions) into a fully textured mesh?

I have already tried exporting the entire model to a .obj but the texture becomes one of the Materials of the parts.

My Model

Model:
image

Contents:
image

Export Attempts

image
image

You can try exporting them separately or export the whole thing as one but you have to manually unwrap all the textures