Lithunwrap will load .3ds models (and many others as well) and save them out to boatloads of formats. You see the problem with .3ds files is that a vertix can only be attached to one face. Therefore if you have a simple cube, rather than having 8 vertices like most other formats, .3ds files will have 48 vertices!!! Lithunwrap has a utility called "Optimize Model" that will find all these duplicated vertices and combine them into a single vertix.
I am a little curious though, what kind of model were you hoping to use in DBPro that takes a 1.6MB .3ds file? In order to have a file of that size, you must have quite a few vertices & polies!!! If you are thinking you can drag some 300000 poly model in DBpro and have any kind of FPS you're sorely mistaken.
Intel Pentium 4, 3.4GHz, 1280MB RAM, NVidia Quadro FX3000/256MB, 240GB HD, XP Pro