Oh man, Dash 3G isn't a device I have seen in a long time!
We don't seem to have anything specific for drivers, this is the best I could find and I am not sure the answer still helps. DRIVER for T-Mobile DASH | Non-Touchscreen Windows Mobile
Just checking in here to see if you found the drivers you needed.
Just wanted to know, have you checked out Lauren's post? Please take a look at that link and let us know if that gave you the help you needed. Thank you!