I'm getting an error stating attempt to index nil with Backpack?

This is a script located in serverscriptservice. All it does is once the gui called "Employer" has been clicked to send items it fires a remote event that will then clone the items from the person using the "Employer" Gui and give them to the person whose name has been written in plrname (plrname is a textbox). Please help! Thanks in advance!

game.Players.PlayerAdded:Connect(function(player)
game.ReplicatedStorage.fyg.OnServerEvent:Connect(function()
	for i,v in pairs(game.Players:GetChildren()) do
		local fu = v:FindFirstChild("PlayerGui")
		local fa = fu:FindFirstChild("Employer")
		local fe = fa:FindFirstChild("Frame")
			local fo = fe:FindFirstChild("plrname")
			local plr = game.Players:FindFirstChild(fo.Text)
			local pack = plr.Backpack
			for i,v in pairs(player.Backpack:GetChildren()) do
				v:Clone().Parent = pack
			end
		end
	end)
end)

EDIT: the script to fire the remote event contains:

script.Parent.MouseButton1Click:Connect(function()
	local event1 = game.ReplicatedStorage.fyg
	event1:FireServer()
if game.ReplicatedStorage.orders.order.Value == 1 then
		game.ReplicatedStorage.orders.order.Value = game.ReplicatedStorage.orders.order.Value -1
	end
end)

You don't need the onserverevent event inside the playeradded event.

game.ReplicatedStorage.fyg.OnServerEvent:Connect(function(plr)
        local fu = plr:FindFirstChild("PlayerGui")
        local fa = fu:FindFirstChild("Employer")
        local fe = fa:FindFirstChild("Frame")
        local pack = plr.Backpack
        for i,v in pairs(player.Backpack:GetChildren()) do
        	v:Clone().Parent = pack
        end
 end)

The event returns the player so you don't need playeradded event to get the player which fired the remoteevent.