This is how you do it (surprised noone have told you yet...):
3ds2unr doesn't use the same frame-definition as #d studio for instance, with an animation, but it thinks that every model in the scene is an animation frame.
That is, every object, not every shape, since different, nonconnected shapes can be a single object.
What to do in 3D studio:
Open the animated file
Locate the button "snapshot" and click it, it looks like a worm of spheres...
in the box that comes up, you click "range"m, fill in on which frame the animation starts (0) and where it ends (x) and how many copies you want (x+1) and the you can select copy or mesh, I think anything works fine...
Press the OK button and you'll se that it have created a lot of new objects, one for each frame in the animation.
This is what 3ds2unr sees as an animation...
Now save it (preferably as a new file) and let 3ds2unr import it.
If there's no other error you will get the message "Imported x frames..."