What is this confusing error and how to fix it? (Read all)

I have a game, and I have this code for purchasing a gamepass. But.... I got this confusing error when I try it. "11:59:59.999 - Players.Player1.PlayerGui.AdvertisementGUI.CoilGears1.LocalScript:6: attempt to index field 'Parent' (a nil value)". My code is:

if game.Players.LocalPlayer.userId > 1 then
    if game.MarketplaceService:PlayerOwnsAsset(game.Players.LocalPlayer, 578580632) then
        script.Parent:Destroy()
    end
end
script.Parent.MouseButton1Click:connect(function()
    game.MarketplaceService:PromptPurchase(game.Players.LocalPlayer, 578580632)
end)

Now, look at line 6.

script.Parent.MouseButton1Click --:connect(function() --I disconnected the code so the syntax isn't confused

Isn't "script" supposed to mean the script? Then why it shows that error? Also btw its a local script.