number finder script is not working as intended help please?

I didn't test this but let's hope it works:

script.Parent.BackGround2.Enter.MouseButton1Click:connect( function()
        local text = script.Parent.BackGround2.OrderNumberHandler.Text
        local number = tonumber(text)

    if number ~= nil then

            print("Number ", number)
            local OrdersHandler = script.Parent.BackGround3

        if number >= 6 or not number then
                 script.Parent.BackGround2.Enter.Text = "Number Not found"
        end
    end
end)

Why your script doesn't work:

script.Parent.BackGround2.Enter.MouseButton1Click:connect( function()
        local text = script.Parent.BackGround2.OrderNumberHandler.Text
        local number = tonumber(text)
        print("Number ", number)
        local OrdersHandler = script.Parent.BackGround3
 if number >= 6 or not number then
     script.Parent.BackGround2.Enter.Text = "Number Not found"
end


        end)

If a string can't be converted into a number, then tonumber() returns nil. If you put something that isn't a number into text then an error occurs at line 6, saying that it can't compare nil to a number value. This is easily fixed by adding an if statement to check if number is equal to nil.