Therefore, a "7z to NDS converter" is just a file extraction tool. Your .nds file is already fully formed inside the .7z archive. Best Free Tools to Extract 7z Files
Repeat steps 1-5, but ensure the extracted .nds file is copied to the root of your microSD card (or a "Games" folder). Eject the card, insert it into your flashcart, and boot the console. 7z to nds converter
This is the actual game file. It is a digital copy of the data inside a physical Nintendo DS cartridge. Emulators and flashcarts read this specific file format to launch the game. Therefore, a "7z to NDS converter" is just