How do i fix this data item saver?

Can u tell what wrong with this script?

local data = game:GetService("DataStoreService"):GetDataStore("Inventory")
game.Players.PlayerAdded:Connect(function(plr)
	local SavedItems = data:GetSync(plr.userId)
	if SavedItems ~= nil then
		for i, v in pairs(SavedItems)do
			if game.ServerStorage.Inventory:FindFirstChild(v) ~=nil then
				local item = game.ServerStorage.Inventory:FindFirstChild(v) :Clone()
				item.Parent = plr:WaitForChild("Backpack")
			end
		end
	end
	plr.CharacterRemoving:Connect(function()
	    plr.Character.Humanoid:UnequipTools()
	end)
end)

game.Players.PlayerRemoving:Connect(function(plr)
	local Table = {}
	for i, v in pairs(plr.Backpack:GetChildren())do
		table.insert(Table,v.Name)
	end
	if Table ~= nil then
		data:Sync(plr.userId,Table)
	end
end)

If wrong...???? can u comment a data item saver/backpack saver for the player? and can u add... when they die they can't loose there items.

When you read and overwrite data your not typing the correct function names.

Reading data

To read data you need to use GetAsync() not GetSync()

Example:

local data = game:GetService("DataStoreService"):GetDataStore("Inventory")

game.Players.PlayerAdded:Connect(function(plr)
	local SavedItems = data:GetAsync(plr.UserId)
end

Saving data

This is the same problem as reading data. You named the functions incorrectly. Sync() is not a function of DataStore. Instead of using Sync() use SetAsync() which will overwrite data.

Example:

game.Players.PlayerRemoving:Connect(function(plr)
    local Table = {}

    for i, v in pairs(plr.Backpack:GetChildren()) do
        table.insert(Table,v.Name)
    end

    if Table ~= nil then
        data:SetAsync(plr.userId,Table)
    end
end)

Here is a re-written version of your script:

local DataStoreService = game:GetService("DataStoreService")
local DataStore = DataStoreService:GetDataStore("Inventory") -- Separate variable

local function Load(plr)
	local key = "plr-"..plr.UserId -- key variable (The way I do it)
	local savedData -- Will be set below

	local success, err = pcall(function()
		-- This makes sure that the script will keep going if it errors
		savedData = DataStore:GetAsync(key) -- GetAsync()
	end  

	-- if datastore failed to read data
	if not success then
		warn("Failed to read data"..tostring(err))
		return -- this will return nil
	end
		
	-- if datastore succeeded 
	if savedData then
		-- if the player has data then load the data

		for i, v in pairs(savedData) do
			if v then
				local item = game.ServerStorage.Inventory:FindFirstChild(v):Clone()
				
				if item then
					item.Parent = plr:WaitForChild("Backpack")
				end
			end
		end
	else
		-- If the player does not have data to be loaded

		local items = {}
		
		local itemsSaving = plr:WaitForChild("Backpack"):GetChildren()

		for i, v in pairs(itemsSaving) do
			if v then
				table.insert(items, v.Name)
			end
		end

		local success, err = pcall(function() -- protected call
			DataStore:SetAsync(key, items) -- SetAsync()
		end
		
		-- if overwriting data failed
		if not success then
			warn("Failed to overwrite data"..tostring(err))
			return
		end
	end
end

local function SaveData(plr)
	local key = "plr-"..plr.UserId -- Again just how I do it
	local items = {}

	local itemsSaving = plr:WaitForChild("Backpack"):GetChildren()
	
	for i, v in pairs(itemsSaving) do
		if v then
			table.insert(items, v.Name)
		end
	end

	local success, err = pcall(function()
		DataStore:SetAsync(key, items) -- SetAsync()
	end
	
	-- failed
	if not success then
		warn("Failed to overwrite data"..tostring(err))
		return
	end
end

-- Calls
game.Players.PlayerAdded:Connect(Load)
game.Players.PlayerRemoving:Connect(SaveData)

Now you might not need to use the pcalls but they sure came in handy to me. NOTE: "THIS SCRIPT IS NOT TESTED. IT COULD THROW ERRORS AND MAY NOT WORK." (Used caps lock not to be mean but to make sure you see that)

I wrote the script above to fix any bugs with your script. It should work just by copying the script but you may have some tweaking to do. Hope this helps!