Help saving data for endings!,How i do this?

I need to save the endings or events that the player did and put a block if that player already completed that or not, something like that,but I can't think of any script to help me with that

You need to use a DataStore to do this. It's more efficient to use a bool instead of a block though.

local DataStoreService = game:GetService("DataStoreService")
local EndingStore = DataStoreService:GetDataStore()
--This function is only for the first time joining--
local SetEndings = function(folder)
	local values = {
		ExampleEnding = {
			Name = "ExampleEnding",
			Value = false,
		}
	}
	for _,ending in pairs(values) do
		local value = Instance.new("BoolValue",Endings)
		value.Name = ending.Name
		value.Value = ending.Value
	end
end

game.Players.PlayerAdded:Connect(function(player)
	local key = player.UserId .. "_Endings"
	--key is basically a password for the save--
	local Endings = Instance.new("Folder",player)
	Endings.Name = "Endings"
	local Retrieve
	--Use a pcall because thats just a normal thing in data stores--
	local success,errormessage = pcall(function()
		Retrieve = EndingStore:GetAsync(key)
	end)
	if success then
		if Retrieve ~= nil then
			--It checks if the data exists because it wont the first time you join the experience--
			for _,ending in pairs(Retrieve) do
				local value = Instance.new("BoolValue",Endings)
				value.Name = ending.Name
				value.Value = ending.Value
			end
		else
			SetEndings(Endings)
			--Calls the function made previously--
		end
	else
		warn(errormessage)
	end
end)

--now for the saving process--
game.Players.PlayerRemoving:Connect(function(player)
	local key = player.UserId .. "_Endings"
	--same key as before--
	local Endings = player:WaitForChild("Endings")
	--the folder already exists--
	local List = {}
	for _,ending in pairs(Endings) do
		local item = {}
		item.Name = ending.Name
		item.Value = ending.Value
		table.insert(List,item)
		--it creates a table of values containing the endings the player has achieved before leaving--
	end
	local Success,errormessage = pcall(function()
		EndingStore:SetAsync(key,List)
	end)
	if Success then
		print("Successfully saved endings")
	else
		warn(errormessage)
	end
end)

This is just an example. I haven't tested it, but its basically how to do it. If you want cubes just set a cube if the ending value is true.