Links

Information on how Minecraft stores worlds:

• https://minecraft.gamepedia.com/Java_Edition_level_format

Information on region files:

• https://minecraft.gamepedia.com/Anvil_file_format
• https://minecraft.gamepedia.com/Region_file_format

There is a wiki article in spigot wiki in how to use Region-Fixer:

• http://www.spigotmc.org/wiki/using-the-minecraft-region-fixer/