I have lots of old work in 3ds format having 2 copies of blender 2.79b and 2.81a is a little annoying going back and forth between the two.
I have encountered the same problem before and you can find the solution at the following thread:
There is nothing under testing it is blank.
The script in 2.82 Alpha is located at the folder …\2.82\scripts\addons_contrib\io_scene_3ds
Copy it to your Blender 2.81 and install it should work fine.
Only imports, no exports?
No export yet. Please refer to the answer by Andrew_Ray in the thread listed above.