Making secret codes in game?

You don't have an end for the function or a ) for the ( on line 17. Tab your code correctly.

= is a completely different thing from ==.

= means "set" or "assign" -- it's a command.

== means "compare?", or "are these the same?" -- it's a question.

ifs and elseifs need to use ==, not =.

== means "are these the same" -- which includes that they are the same type of thing. Text is a string (the type of text) while code1, etc are numbers.

They have to be the same type -- "100" == 100 is false.

The simplest solution would be to change the definition of code1 etc to use strings:

code1 = "1643543"

Your code is really repetitive.

The big tree of elseifs could be changed into a neat little dictionary.

A dictionary turns keys (in this case, it would be the codes) into values (in this case, it would be the weapons).

Defining a dictionary looks like this:

codes = {
	["1643543"] = game.ReplicatedStorage.Weapon1,
	["3728492"] = game.ReplicatedStorage.Weapon2,
	["5638593"] = game.ReplicatedStorage.Weapon3,
	["5483759"] = game.ReplicatedStorage.Weapon4,
	["4759485"] = game.ReplicatedStorage.Weapon5,
	["4739583"] = game.ReplicatedStorage.Weapon6,
}

Now you can just check if there is actually a weapon for a given code:

codes = {
	["1643543"] = game.ReplicatedStorage.Weapon1,
	["3728492"] = game.ReplicatedStorage.Weapon2,
	["5638593"] = game.ReplicatedStorage.Weapon3,
	["5483759"] = game.ReplicatedStorage.Weapon4,
	["4759485"] = game.ReplicatedStorage.Weapon5,
	["4739583"] = game.ReplicatedStorage.Weapon6,
}

textButton = game.Players.LocalPlayer.PlayerGui.ScreenGui.TextButton
textBox = game.Players.LocalPlayer.PlayerGui.ScreenGui.TextBox
backPack = game.Players.LocalPlayer.Backpack

textButton.MouseButton1Down:connect(function()
	local weapon = codes[ textBox.Text ]
	if weapon then
		-- if the weapon exists (because they entered a real code)
		weapon:Clone().Parent = backPack
	end
end)