How do I make a level up system?

I was trying to make a level up system, where if you reach 100 EXP then you get an extra level, but it doesn't work.

Script

if player.leaderstats.Level.EXP.Value >= player.leaderstats.Level.Max then
	player.leaderstats.Level.EXP.Value = 0
	player.leaderstats.Level.Value = player.leaderstats.Level +1
end

Please help.

If Level.Max is a NumberValue or another ValueBase you need to check the Value of this Instance. Like that: Level.Max.Value

Try this

if (player.leaderstats.Level.EXP.Value >= player.leaderstats.Level.Max.Value) then
    player.leaderstats.Level.EXP.Value = 0
    player.leaderstats.Level.Value += 1
end

Hope this help, to more questions put bellow on commentaries.

ok, so this is not that hard to do. There is something called "Changed" this event happens whenver the number value is changed, you can find the artical here:

https://developer.roblox.com/en-us/api-reference/event/NumberValue/changed

script:

--====================these are just the leveling requirments=============
game.Players.PlayerAdded:Connect(function(player)
	local leaderstats = Instance.new("Folder", player)
	leaderstats.Name = "leaderstats"
	
	local exp = Instance.new("IntValue", player)
	exp.Name = "Exp"
	
	local max = Instance.new("IntValue", player)
	max.Name = "Max"
	max.Value = 100
	
	local level = Instance.new("IntValue", leaderstats)
	level.Name = "Level"
	level.Value = 1
--============================Below is leveling detector===================	

	exp.Changed:Connect(function(value) -- changed function
		print("expValue Changed") -- prints whenever you get more exp
		if value == max.Value then --if the exp is bigger than the max exp
			exp.Value = 0 -- resetting the exp to 0 after leveled up
			level.Value += 1 -- adding one more level
			max.Value += 50 --every time you level up, you will need 50 more exp to level up again
			print("YAY U LEVELED UP!!")
		end
	end)
end)