How do I code a Dev. Product script that...?

--Put this script in ServerScriptService.
--TIP: Press F9 during game for debugging.
local MarketplaceService = Game:GetService("MarketplaceService")

local currency = "Points" --Change

--Forces save to ensure no loss of data.
function SaveStats(player)
    player:SaveNumber(currency, player.leaderstats:FindFirstChild(currency).Value)
end

-- IDs (Change the numbers to match the IDs of your developer products. You may copy more.)
local productId01 = 000000
local productId02 = 000000
local productId03 = 000000
local productId04 = 000000

MarketplaceService.ProcessReceipt = function(receiptInfo)
    --local playerProductKey = "player_" .. receiptInfo.PlayerId .. "_Points"
    local Player = Game.Players:GetChildren()
    for i = 1, #Player do
        if Player[i].userId == receiptInfo.PlayerId then
            prodId = tonumber(receiptInfo.ProductId)
            local h = Instance.new("Hint", Player[i])
            --Purchase Points. Change the numbers however you desire.
            if prodId == productId01 then
                Player[i].leaderstats:FindFirstChild(currency).Value = Player[i].leaderstats:FindFirstChild(currency).Value + 25
            elseif prodId == productId02 then
                Player[i].leaderstats:FindFirstChild(currency).Value = Player[i].leaderstats:FindFirstChild(currency).Value + 120
            elseif prodId == productId03 then
                Player[i].leaderstats:FindFirstChild(currency).Value = Player[i].leaderstats:FindFirstChild(currency).Value + 375
            elseif prodId == productId04 then
                Player[i].leaderstats:FindFirstChild(currency).Value = Player[i].leaderstats:FindFirstChild(currency).Value + 1337
            else
                h.Text = "Something went wrong."
                Game:GetService("Debris"):AddItem(h, 4)
                print("Something went wrong.")
                wait(1)
            end
            SaveStats(Player[i])
            h.Text = "Your points have been saved! Thank you for purchasing!"
            Game:GetService("Debris"):AddItem(msg, 4)
        end
    end

    return Enum.ProductPurchaseDecision.PurchaseGranted
end