Hi Marilyn
If it's any help to you, the USB reader/writer included with the KN7000 in the UK is:-
"the Panasonic SZ-CB7 SD Audio PC writing kit for Technics SX-KN7000" which also includes the SD-Jukebox V2.4 for recording audio files.
It sounds as though your SD card is OK, but I've got a feeling (and I hope I'm wrong) that your USB reader/writer may not be compatible with the KN7000. It could be be that it is reading/writing but the KN7000 cannot see the files. You could try formatting the SD card; taking note afterwards of the space in Kbytes left on the SD card and then using restore and then checking if the remaining space has changed.
John