Make a real backup
A backup must contain your saved world progress. For Java Edition, use the world-management backup option and retain the resulting archive somewhere you can identify. Give important backups a useful date or milestone label and check that the copy exists before modifying the original.
Use your platform’s supported method
Bedrock backup and recovery steps differ between Windows, mobile, consoles and Realms. Follow the instructions for the device actually holding the world. Keep the game closed when a platform’s file-copy instructions require it, and avoid overwriting your only copy while testing a restore.
A seed is not a saved game
A seed can recreate a familiar starting map under matching generation rules; it does not restore your constructions, inventory or progress. If recovery is needed, try a suitable backup first and preserve the damaged or newer original until you have checked the restored copy.