Problem with adding a value to a folder in a player that has just been created?

Okay, so everything is being created in the inventory when I buy the item the first time, but the second time I want to buy the item, I just want it to add 1 to a value that's in the item, but I keep getting this:
14:40:02.823 - Players.rak553.PlayerGui.aShop.ShopFrame.BuyFrame.BuyButton.Buy:30: attempt to index field 'ItemAmount' (a nil value)

This is the broken line:

Inventory.name.ItemAmount.Value = Inventory.name.ItemAmount.Value + 1

That's the whole code, please help me!

local plr = game.Players.LocalPlayer
local button = script.Parent

local Item = Instance.new('Folder')
local ItemType = Instance.new('StringValue')
local ItemAmount = Instance.new('NumberValue')
local moneyAmount = plr.Money.Amount.Value
local Inventory = plr.Inventory

button.MouseButton1Click:connect(function()
local price = script.Parent.Price.Value
local name = script.Parent.ItemName.Value
local typeName = script.Parent.ItemType.Value

if (moneyAmount >= price) then
    moneyAmount = moneyAmount - price
    if (not Inventory:FindFirstChild(name)) then
        --Create Item
        Item.Parent = Inventory
        Item.Name = name
        --Create Item Type and Set it
        ItemType.Parent = Item
        ItemType.Name = "ItemType"
        ItemType.Value = typeName
        --Create ItemAmount and Set it
        ItemAmount.Parent = Item
        ItemAmount.Name = "ItemAmount"
        ItemAmount.Value = 1
    else
      Inventory.name.ItemAmount.Value = Inventory.name.ItemAmount.Value + 1
       end
    end
end)