Roblox DataStore is free but limited. External saving costs real money. For most developers, external saves only make sense for games with >10,000 DAU or unique data needs.
Before understanding the "how," you must understand the "why." Roblox’s built-in DataStore is powerful, but it has limitations: Roblox save instance -EXTERNAL-
Because server scripts are missing, the saved game will almost never "run" or function correctly without significant rebuilding. Roblox DataStore is free but limited