If they were entered and saved in nRoute, they should be in a gdb file. If not, open the nRoute file and export to a gdb file. You can open this in MapSource and use the 'Send to Device' function to move the waypoints to Mobile PC. If you have a version of MapSource newer than 6.13.7 make sure you update it to the latest 6.15.6 from the Garmin site.
The first time you use the Send to Device function, you may have to have Mobile PC running so MapSource can find it. Future transfers do no need this step.
Terry