I am trying to update maps on a new Kenwood DNR1007XR.

I do not know anything about the Kenwood DNR1007XR so researched it as well as the instructions you provided.  If you are getting some sort of messages saying 'the path does not exist' when you do the Settings > Device > Update Map procedure then I suspect that the SD card is in not being recognized.  The instructions say to format it but they don't specify the file system to format it as.  I suggest that you insure it is formatted as FAT32 which is the most compatible, and is know to be required for SD cards used in other Garmin navigation devices.