How do I make a function with a mouse button click with a server script?

This is my code inside the button

function Convert()
	local plr = game.Players.PlayerAdded:Wait()
	if plr.Leaderstats.Convert.Value > plr.Leaderstats.Robux.Value then
		script.Parent.Parent.ConvertBox.Text = "Invalid conversion amount!"
		wait(2)
		script.Parent.Parent.ConvertBox.Text = ""
	else
plr.Leaderstats.Tix.Value-=plr.Leaderstats.Convert.Value
		plr.Leaderstats.Robux.Value+=plr.Leaderstats.FinalConvert.Value
	end
end

script.Parent.MouseButton1Click:Connect(Convert)

this is all inside a server script. This is because my data store wont work if it is a local script. How would I fix this so it can stay inside a server script?

Sorry bud but you really need a LocalScript in order for the button to work. To make your data store work, you can use a RemoteEvent to change the value in server and a RemoteFunction to get the value of the player from the server (because if you get it to the client it might not be the same to the server since hackers can change anything ONLY to the client).

First, you create a RemoteEvent and a RemoteFunction inside ReplicatedStorage. Name the RemoteEvent SetValue and the RemoteFunction GetValue.

Next, you will create a script in ServerScriptService and name it RemoteHandler.

Then, you will create a listener for SetValue and a callback function for GetValue in RemoteHandler.

local ReplicatedStorage = game:GetService("ReplicatedStorage")
local GetValue = ReplicatedStorage.GetValue
local SetValue = ReplicatedStorage.SetValue

GetValue.OnServerInvoke = function(player, valueName)
	local leaderstats = player:FindFirstChild("Leaderstats")
	if leaderstats then
		local value = leaderstats:FindFirstChild(valueName)
		if value then -- if it exists
			if value:IsA("ValueBase") then
				return value.Value
			end
		end
	end
end

SetValue.OnServerEvent:Connect(function(player, valueName, valueSet)
	local leaderstats = player:FindFirstChild("Leaderstats")
	if leaderstats then
		local value = leaderstats:FindFirstChild(valueName)
		if value then -- if it exists
			if value:IsA("ValueBase") then
				value.Value = valueSet
			end
		end
	end
end)

Lastly, you can use them in the LocalScript and it should look like this:

local ReplicatedStorage = game:GetService("ReplicatedStorage")
local GetValue = ReplicatedStorage:WaitForChild("GetValue")
local SetValue = ReplicatedStorage:WaitForChild("SetValue")

function Convert()
	if GetValue:InvokeServer("Convert") > GetValue:InvokeServer("Robux") then
		script.Parent.Parent.ConvertBox.Text = "Invalid conversion amount!"
		task.wait(2)
		script.Parent.Parent.ConvertBox.Text = ""
	else
		SetValue:FireServer("Tix", (GetValue:InvokeServer("Tix") - GetValue:InvokeServer("Convert")))
		SetValue:FireServer("Robux", (GetValue:InvokeServer("Robux") + GetValue:InvokeServer("FinalConvert")))
	end
end

script.Parent.MouseButton1Click:Connect(Convert)

local plr=script:FindFirstAncestorOfClass("Player")