I made this random Terrain Maker Plugin but i get error; 'for' limit (number expected, got nil)?

i am trying to make this Random Terrain Maker Plugin but the every time i run the plugin button it seems to not work!.

Error name:

user_C:/Users/U1/Downloads/IDK.rbxmx.Folder.Main:51: invalid 'for' limit (number expected, got nil)

My Code:

local Maingui = script.Parent.ScreenGui.MainFrame
local plugbutton = plugin:CreateToolbar("N/A"):CreateButton("N/A","N/A","N/A")
local ScreenGui = script.Parent.ScreenGui
local X_Button = Maingui.Topbar.Exit_Program
local Create_Terrain_Button = Maingui.Create
local INPUTS = Maingui.Inputs
local MapX = INPUTS.MXS
local MapY = INPUTS.MYS
local MapZ = INPUTS.MZS
local NS = INPUTS.NS

local MapX2 = tonumber(INPUTS.MXS)
local MapY2 = tonumber(INPUTS.MYS)
local MapZ2 = tonumber(INPUTS.MZS)
local NS2 = tonumber(INPUTS.NS)


isOn = false

ScreenGui.Parent = game.CoreGui

Maingui.Active = true
Maingui.Selectable = true
Maingui.Draggable = true

-- Terain Maker Main Code

function TerrainMaker(X,Y,Z,noisescale)
	local Folder = Instance.new('Folder',game.Workspace)
	Folder.Name = "TerrainFolder"
	wait(0.5)	
	local mapxsize = X
	local mapysize = Y
	local mapzsize = Z
	local seed = math.random(1,100000)
	local noisescale = noisescale
	local amp = 15
	local psize = 2

	for x=0,mapxsize do -- This is Where i get the Error!
		for z=0,mapzsize do
			for y=0,mapysize do
				local xnoise = math.noise(y/noisescale,z/noisescale,seed)*amp
				local ynoise = math.noise(x/noisescale,z/noisescale,seed)*amp
				local znoise = math.noise(x/noisescale,y/noisescale,seed)*amp
				
				local density = xnoise+ynoise+znoise+y
				if density < 20 and density > 15 then
					local part = Instance.new("Part",workspace.TerrainFolder)
					part.Anchored = true
					part.Size = Vector3.new(psize,psize,psize)
					part.CFrame = CFrame.new(x*psize,y*psize,z*psize)
					if part.Position.Y >= 59 then
						part.BrickColor = BrickColor.new("Medium stone grey")
						part.Material = ("SmoothPlastic")
						
					else
						part.BrickColor = BrickColor.new("Bright green")
						part.Material = ("Grass")
					end
				end
			end
		end
		wait(0.5)
	end	
end





Create_Terrain_Button.MouseButton1Click:Connect(function()
	if MapX.Text == "" or MapY.Text == "" or MapZ.Text == "" or NS.Text == "" then
		print("Please Provide all information Needed!")
		
	else
		TerrainMaker(MapX2,MapY2,MapZ2,NS2)
		
		
	end
end)


plugbutton.Click:Connect(function()
	isOn = not isOn
	plugbutton:SetActive(isOn)
	ScreenGui.Enabled = isOn
end)

any Reason why?

INPUTS.MXS,INPUTS.MYS,INPUTS.MZS are text box's

Is there a Way to fix my code?

local MapX2 = tonumber(INPUTS.MXS)
local MapY2 = tonumber(INPUTS.MYS)
local MapZ2 = tonumber(INPUTS.MZS)

After narrowing down the origin of your axes, these three lines are all most likely nil. This would be because INPUTS.MXS, INPUTS.MYS, and INPUTS.MZS cannot be converted into numbers.