Not a valid Backpack member

I am doing an inventory system and I want a gui to be triggered when an object is detected in the inventory. but it appears to me that backpack is not a valid member. this is the code

local Classic = game.ReplicatedStorage.Library.ClassicSword

local Fire = game.ReplicatedStorage.Library.FireSword

local super = game.ReplicatedStorage.Library.SuperSword

local gold = game.ReplicatedStorage.Library.GoldSword

local rain = game.ReplicatedStorage.Library.RainBow

local soword = game.ReplicatedStorage.Library.SwordofStarlight

local devil = game.ReplicatedStorage.Library[“Devil Sword”]

local CGUI = script.Parent.Classic

local FGUI = script.Parent.Fire

local SGUI = script.Parent.Super

local GGUI = script.Parent.Golden

local RGUI = script.Parent.Raimbow

local SSGUI = script.Parent.Starlinhgt

local DGUI = script.Parent.devil

local player = script.Parent.Parent.Parent.Parent

local CS = player.Backpack.ClassicSword

local FS = player.Backpack.FireSword

local SS = player.Backpack.SuperSword

local GS = player.Backpack.GoldSword

local RS = player.Backpack.RainBow

local STS = player.Backpack.SwordofStarlight

DS = player.Backpack[“Devil Sword”]

if CS then

CGUI.Visible = true

elseif FS then

FGUI.Visible = true

elseif SS then

SGUI.Visible = true

elseif GS then

GGUI.Visible = true

elseif RS then

RGUI.Visible = true

elseif STS then

SSGUI.Visible = true

elseif DS then

DGUI.Visible = true

end

Could you use the Lua format for your code for the sake of clarity?

Try doing:
print(player.Name)

always use WaitForChild()
like i.e.:

 player.Backpack:WaitForChild("ClassicSword")

change other repective codes as well