InDesign always has function that allowed users to export their documents so they are compatible with previous version. This was done when the InDesign document was saved as .inx files. Latest InDesign replaced .inx files with .idml files but share the same purpose and is no longer used.
So the only way to generate .inx files would be to use InDesign CS4 or earlier, but preferably CS4. You also need the latest dot release installed to prevent errors or other issues when opening the document.