Hi David,
You can do a 'backup' which will copy the contents (all music) of the JB7 to the USB stick BUT the stick needs to have sufficient memory to take the backup in one go.
You can check the 'disk stats' on the JB7 to see how much memory space has been used and hence how big the USB stick needs to be.
The backup command is in the 'USB menu' and disk stats is in the 'Main menu'.
Paul
Brennan Support.