How do I make it so when a brick is touched an item is removed from the inv?

I'm trying to make it so a player can grab a box and bring it to a destination.. (I'm a noob to scripting) I would like to add "1" to a NumberValue when a box is delivered (I'd also like to remove the Box from the inventory after touch) this is what I have:

local debounce = false

script.Parent.Touched:Connect(function(hit)
    if not debounce then
        debounce = true
        local plr = game:GetService("Players"):GetPlayerFromCharacter(hit.Parent)
        if plr then
            local holders = {plr:FindFirstChild("Backpack"), plr:FindFirstChild("StarterGear"), hit.Parent}
            game.Workspace.itemStocks.numberofSoap = game.Workspace.itemStocks.numberofSoap + 1
            for i,v in pairs(holders) do
                pcall(function()
                    for i,v in pairs(v:GetChildren()) do
                        if v:IsA("BackpackItem") then
                            v:Destroy()
                        end
                    end
                end)
            end
        end
        wait(60)
        debounce = false
    end
end)

However I get an error in the output saying "20:47:44.955 - Workspace.End.Script:10: attempt to perform arithmetic on field 'numberofSoap' (a userdata value)"