I don't know for sure if this will work because I've never tried it but:
-Download and install GTK Radiant (you'll need Quake III)
-right click in the main top-down window
-select 'misc'
-select 'misc_model'
-select Files Of Type '3ds file(*.3ds)'
This should open your 3DS Model. Then it's just a matter of saving to a .map file or exporting to a .bsp.
Hope this helps.
RV
-Download and install GTK Radiant (you'll need Quake III)
-right click in the main top-down window
-select 'misc'
-select 'misc_model'
-select Files Of Type '3ds file(*.3ds)'
This should open your 3DS Model. Then it's just a matter of saving to a .map file or exporting to a .bsp.
Hope this helps.
RV