Convert from 3D home architect to Design Suite 8 Deluxe?
Although I have never used those programs: If the programs themselves don't offer the ability to open up a file from their competition then most likely the binary file format is proprietary and you are not going to be doing any conversion.
Simply create a test file in 3D HA and try opening it with the standard File Open in DS 8D. If it doesn't open you are most likely out of luck.