Hi Larry,
Welcome back to your KN7000 - still a really great keyboard.....
I wonder if you got a copy of the 'Applications and Drivers' CD with the keyboard? It has all the necessary programs to allow you to use the SD Card system with a PC via USB. Unfortunately, these programs were written in the early 2000s and will only work on a PC with Windows 98 or Windows XP, which of course were the PC operating systems at that time. I just tried to install the software on one of my Windows 10 PCs but No-Go.
The way I get around this - I have a small ACER 10 inch Notebook with Windows XP installed, and this sits on the music rest of my KN7000 and is permanently connected via USB to my KN7000 and to my home network. So any files are downloaded to the ACER and can then be easily transferred to and from the KN7000 SD Card.
If you can find a Netbook or Laptop to install XP then this would be an ideal solution...
There is a very useful program called KN7000 SD Explorer which allows editing/ manipulation of KN7000 data on an SD Card, and works OK on versions of Windows up to and including Win 10. It was written by a Dutch guy and you can contact him here :
https://wf.mellink.info/contact-nl As Roger said, you can only use standard SD Cards up to a capacity of 2 Gb. The KN7000 only actually recognises cards up to 1Gb but tolerates cards up to 2 Gb but only uses 1 Gb of the card's capacity. Even a 1 Gb card really takes a lot of filling with KN7000 files!
If all else fails Larry, you could always buy an external Floppy drive which connects to your PC via USB. You'll find them with a search on the internet..... Also Floppy discs are still available... See Amazon...