The world should now appear in your single-player menu. Why use .7z for Minecraft? How to BACKUP your Minecraft World! 1.21.4 (Java Edition)
The file is a compressed archive containing a backup of a Minecraft world or server, created using the 7-Zip utility . While the name contains a small typo ("Minceaft" instead of "Minecraft"), it follows the standard practice of using high-ratio compression to protect large game files from corruption or data loss. What is inside Minceaftbackup.7z? Minceaftbackup.7z
This archive typically holds all essential data required to restore a specific state of your game: The world should now appear in your single-player menu