Maximillions WBFS GUI v2 will allow you to copy all of your Wii ISO’s onto your USB drive ready for use with USB Loader.
Simply copy wbfs_win.exe to your PC’s system32 directory, then run the Maximillions WBFS Gui.exe.
As well as copying ISO’s from PC – USB Drive it also compresses them, saving you a lot of space. You can also copy the ISO back from the USB drive to your PC as well.