Which USB mode did you use to put them on? If you used MTP then they are not where you expect, and to see them you need to use the Rockbox database. Much easier is to use UMS mode and just copy and paste. Note that if you put them in the Music folder, if you boot the OF it will set it to hidden.
Also:
Please don't double post
Please try to keep a thread on it's subject
This isn't an installation question