John,
The new waypoints should have been saved to the SD card along with all of the other waypoints, tracks and routes that were already in your unit. These should be in the DATA.HWR file that is in the MATRIX folder on the SD card.
Once you open the DATA.HWR file in HumminbirdPC you can save it as a *.gpx file with whatever name you choose for it. The data may than be readable with another program if you are needing it in ASCII but I do not know of one that does. You should be able to see the coordinates for each waypoint in HumminbirdPC though.