There isn't one for AB3D 1.
Some years ago I did some investigation into the level file format and managed to get the wall structures converted to Quake 1 ".map" format. But I didn't get the whole format figured out (eg: switches, items, aliens etc.) as it turned out the Quake 1 engine couldn't handle the level size AB3D required and I abandoned the project.
That's as far as anyone has got, as far as I know.