If you do not have a physical Wii, you can use Dolphin’s built-in feature to download a "clean" set of system files directly from Nintendo’s servers. Go to Tools > Perform Online System Update . Select your preferred Region (USA, JPN, EUR).
Complete Guide to Wii NAND and Dolphin Emulator: Setup, Downloads, and Best Practices wii nand download dolphin top
For the most authentic experience—including your specific Miis, save data, and purchased Shop Channel content—you can dump the NAND from a physical Wii console. Requirements : A homebrewed Wii with installed. Launch BootMii on your Wii. If you do not have a physical Wii,