Sorry for the confusion. In the beginning, SOME files did show up on the Zumo, but were totally random. That's what led me to clean it all out. After I did that, My Zumo showed no tracks available, and when I went to import there were no files to import.
So, then I tried transferring to GPX in ...

Thanks for your help so far! I tried internal storage, that didn't work. I deleted them, then tried the card, and didn't work either.
I transferred several files at the same time, and verified these files work. ( I used GPX studio )

I'm about ready to pitch this thing. I went into the Zumo and on my computer and deleted every GPX file that was anywhere. Completely cleaned out. Internal storage and memory card, every subfolder I checked. When I was done there were no tracks in the Garmin tracks file, and no files to import.
So ...

"When you copy to the SD card are you putting them in a Garmin/GPX directory, or a subdirectory of the Garmin/GPX directory?"
I've tried both. Both will show in the directory when checked on my PC....

"Also, all routes and tracks on the SD card will remain available for import until you use a file ...

Well, I posted a question regarding transferring tracks to a Mac and found out what I have to do with that. But, now I'm having trouble with my PC...I can drag and drop or copy and paste tracks created on my computer directly into the GPX folder on the internal storage. I can do the same directly to ...

I have a PC at work. I can transfer GPX tracks from my computer to the Garmin all day long. But, I have a Mac at home. When I connect the USB up to it the Garmin goes into file transfer mode (just like when I hook up to the PC) BUT it never shows up on the Mac. I can take the micro SD card out of ...