Transferring a single number from one place to another

Currently, I’m trying to implement a loadout system into my game.

The game is split into two places:

Place A → Main menu

Place B → Main game

The loadout is determined by an attribute labelled as “LoadoutID”, which is set in Place A as a single digit, and I need to transfer LoadoutID’s value into Place B.

You could use a datastore.

Are you using TeleportService? Most TeleportService functions allow you to send data with the player.

These might be of use to you:
https://developer.roblox.com/en-us/api-reference/function/TeleportService/GetArrivingTeleportGui
https://developer.roblox.com/en-us/api-reference/function/TeleportService/GetLocalPlayerTeleportData