"create a script where there are leaderstats called Money and it will save when you leave and rejoin the game"

-- local script (StarterPlayerScripts) 
local DataStoreService = game:GetService("DataStoreService")
local MoneyStore = DataStoreService:GetDataStore("MoneyData")
local Players = game:GetService("Players")

local function onPlayerAdded(player)
    local leaderstats = Instance.new("Folder")
    leaderstats.Name = "leaderstats"
    leaderstats.Parent = player

local Money = Instance.new("IntValue")
    Money.Name = "Money"
    Money.Parent = leaderstats

local savedData
    local success, err = pcall(function()
        savedData = MoneyStore:GetAsync(player.UserId)
    end)

if success and savedData then
        Money.Value = savedData
    else
        Money.Value = 0
    end
end

local function onPlayerRemoving(player)
    local success, err = pcall(function()
        MoneyStore:SetAsync(player.UserId, player.leaderstats.Money.Value)
    end)

if not success then
        warn("Failed to save data for player " .. player.Name)
    end
end

Players.PlayerAdded:Connect(onPlayerAdded)
Players.PlayerRemoving:Connect(onPlayerRemoving)