my datastore not working, i don't know how to solve the problem?

Well, there are few flaws in your datastore code.

Flaws:

1. You are assuming a string as a table, which is data.

2. You are not assigning a variable for the returning function in pcall().

3. There is no BindToClose function.

4. You are not checking whether the data exists or not (for new players).

Possible solutions :

1. Do what, @TheMinecraftSmarts have said :

local data
local success, errormessage = pcall(function()
    data = DataStore:GetAsync(key)
end)

1. Check whether the data exists :

if success and data then -- It will ensure whether the data is not nil and exists

1. Make a default value :

-- Instead of 
Coins.Value = data[1]

-- Make it
Coins.Value = 0 -- or whatever value you want to have for new players

1. If the data exists, give the coins saved in the data :

if success and data then
	Coins.Value = data[1]
else
	warn(errormessage)
end

1. Add a BindToClose function :

local RunService = game:GetService("RunService")

game:BindToClose(function()
	if RunService:IsStudio() then return end
	for _, plr in ipairs(game.Players:GetPlayers()) do
		-- Your code for saving data
	end
end)

What's the full output code after edits?

1. For testing in Studio, it should be like :

local RunService = game:GetService("RunService")
local DataStoreService = game:GetService("DataStoreService")
local DataStore = DataStoreService:GetDataStore("PlayerData")

game.Players.PlayerAdded:Connect(function(plr)

    local key = plr.UserId.."Key"

	local data
    local success, errormessage = pcall(function()
        data = DataStore:GetAsync(key)
    end)

    local folder = Instance.new("Folder", plr)
    folder.Name = "stats"

    local Coins = Instance.new("NumberValue", folder)
    Coins.Name = "Coins"
    Coins.Value = 0 -- As example

    print(data[1])

	if success and data then
		Coins.Value = data[1]
	else
		warn(errormessage)
	end

    workspace.Coin.OnServerEvent:Connect(function(plr, add)
        Coins.Value = Coins.Value + 1
    end)
end)

--[[ game.Players.PlayerRemoving:Connect(function(plr)
    local key = plr.UserId.."Key"

    local data = {
        plr.stats.Coins.Value

    }

    local success, err = pcall(function()
        DataStore:SetAsync(key, data)
    end)

end) ]]

game:BindToClose(function()
--	if RunService:IsStudio() then return end
	for _, plr in ipairs(game.Players:GetPlayers()) do
		local key = plr.UserId.."Key"

    		local data = {
        		plr.stats.Coins.Value

   		 }

    		local success, err = pcall(function()
        		DataStore:SetAsync(key, data)
   		end)
	end
end)

1. For Roblox Real server (during publish) :

local RunService = game:GetService("RunService")
local DataStoreService = game:GetService("DataStoreService")
local DataStore = DataStoreService:GetDataStore("PlayerData")

game.Players.PlayerAdded:Connect(function(plr)

    local key = plr.UserId.."Key"

	local data
    local success, errormessage = pcall(function()
        data = DataStore:GetAsync(key)
    end)

    local folder = Instance.new("Folder", plr)
    folder.Name = "stats"

    local Coins = Instance.new("NumberValue", folder)
    Coins.Name = "Coins"
    Coins.Value = 0 -- As example

    print(data[1])

	if success and data then
		Coins.Value = data[1]
	else
		warn(errormessage)
	end

    workspace.Coin.OnServerEvent:Connect(function(plr, add)
        Coins.Value = Coins.Value + 1
    end)
end)

game.Players.PlayerRemoving:Connect(function(plr)
    local key = plr.UserId.."Key"

    local data = {
        plr.stats.Coins.Value

    }

    local success, err = pcall(function()
        DataStore:SetAsync(key, data)
    end)

end) 

game:BindToClose(function()
	if RunService:IsStudio() then return end
	for _, plr in ipairs(game.Players:GetPlayers()) do
		local key = plr.UserId.."Key"

    		local data = {
        		plr.stats.Coins.Value

   		 }

    		local success, err = pcall(function()
        		DataStore:SetAsync(key, data)
   		end)
	end
end)

Lemme know if it helps!