I don't know if/what the previous app or plugin was. Anim8or only exports to the .3ds and .an8 format for animated sequences or scenes.
I had time to burn, so I created a macro-based toolset that'll do all the manual work for you.
How to use:
- Install Blender
- Extract the attached .zip file to its own directory
- Open your Anim8or project, and go to the scene or sequence that you want to export
- Open "Sequential .OBJ Export.exe" from the .zip file
- If the program can't find blender, it'll ask you where it's located
- Indicate the location and name that you want to save the sequence of 3ds files
- Indicate whether you're saving a scene or a sequence
- Wait patiently for it to export each frame automatically
- When it's complete, it'll run the convert_3DS.bat file that batch converts it all to .obj in the same directory
Let me know if it helps, or if you have issues. I chose blender for the conversion since there wasn't anything else that I could find, but technically if you had software that could batch convert 3ds files, you could use that instead.
--Note that 3ds has a vertex limitation of around 65k