You cannot drag a .7z file into an SD card and play it on a Wii. You must and convert it. Hence, the need for a "7z to WBFS converter."
A specialized file format that stores Wii games, stripping out unnecessary data to significantly reduce file size (a 4GB game might become 1GB or less). Best 7z to WBFS Converter Tools
Because .7z is a compressed archive and not a disk image itself, you cannot directly "convert" it to .wbfs with a single click. The process always involves two distinct stages:
Wii Backup Manager is the gold standard software for Windows. It reads ISO or WBFS files, formats your USB drive correctly, scrubs filler data, and transfers the games into the exact folder structure your Wii requires. Step-by-Step Tutorial: How to Convert 7z to WBFS