attempt to index a nil value? Need help please?

This script would work with leaderstats. However we switched to a datastore in order to save data (obviously). However, with the data store, it doesnt work. Instead the script shows this error:

attempt to index a nil value (LINE 4 & 15)

If you find a fix for this please help me. Been trying for 2 hours. Heres some information:

CurrentBackpack is a string value that is in the player. (EXAMPLE: game.Players.LocalPlayer:FindFirstChild("CurrentBackpack"))

CurrentBP.Value is just the string value of the Current Backpack. Examples are: SmallBackpack, MediumBackpack, Etc). In here it gets for example SmallBackpack and finds it in ReplicatedStorage to clone into the player

game.Players.PlayerAdded:connect(function(plr)
	plr.CharacterAdded:connect(function(character)
		local CurrentBP = plr:WaitForChild("CurrentBackpack")
		local FirstBp = game.ReplicatedStorage.GameObjects.Backpacks:FindFirstChild(CurrentBP.Value):Clone()
		print(FirstBp)
		FirstBp.Parent = character
		FirstBp.Name = "Backpack"		
		
		
		
		
		
		plr:WaitForChild("CurrentBackpack").Changed:connect(function(value)
			print(value)
			local NewBackpack = game.ReplicatedStorage.GameObjects.Backpacks:FindFirstChild(plr.CurrentBackpack.Value):Clone()
			character:FindFirstChild("Backpack"):Destroy()
			NewBackpack.Parent = character
			NewBackpack.Name = "Backpack"
		end)
	end)
end)