I agree with MacJunky - the MP110 doesn't need a dongle - just connect using a standard Mac printer cable into whatever port on the Mac you are not using already (printer/modem).

If you are using the 6500, check out http://www.unna.org/view.php?/apple/connection_utils/ForMac for the connection software (and the rest of the site for other Newton software).

Hope you get it working!