Why wont this music button script play the music?

I have been trying for a couple hours to do this and it just wont work at all

one error occurred that says: Players.TheGrimDeathZombie.PlayerGui.MainMenu.Options.OptionsFrame.Main:2: attempt to concatenate field 'PUserId' (a userdata value)

the script is here:

local PrefMusicStore = game:GetService('DataStoreService'):GetDataStore('PrefferedMusic')
local PrefMusic = PrefMusicStore:GetAsync('User_'..script.Parent.PUserId)
if PrefMusic == nil then
    PrefMusicStore:SetAsync('User_'..script.Parent.PUserId, "Creative6")
    script.Parent.Parent.Parent.Creative6:Play()
else
    script.Parent.Parent.Parent:FindFirstChild(PrefMusic):Play()
end

script.Parent.M1.MouseButton1Click:connect(function()
    local Items = script.Parent.Parent.Parent:GetChildren()
    for index, value in ipairs(Items) do
        if value:IsA('Sound') then
            value:Stop()
        end
    end
    wait(.1)
    script.Parent.Parent.Parent.Creative6:Play()
    PrefMusicStore:SetAsync('User_'..script.Parent.PUserId, "Creative6")
end)

script.Parent.M1.MouseButton1Click:connect(function()
    local Items = script.Parent.Parent.Parent:GetChildren()
    for index, value in ipairs(Items) do
        if value:IsA('Sound') then
            value:Stop()
        end
    end
    wait(.1)
    script.Parent.Parent.Parent.Damage:Play()
    PrefMusicStore:SetAsync('User_'..script.Parent.PUserId, "Damage")
end)