I actually found a way, now it will be useless but im still saying. If you download FTPiiU Everywhere you can access storage_usb from an FTP app. You can find your games into the titles folder.
Sadly, I don't know any way to convert them either. Just use Wii U USB Helper AND WUP Installer GX2 to install the games! (The USB must be formatted in wii u settings)