How would I make a value like 03 using the variable value itself? [closed]

Does anyone know how I would make something like 03 using a 0, then the variable next to it? This is my current script

local timer = script.Parent
local minutes = 10
local seconds = 0
local milliseconds = 0

repeat
    if milliseconds < 9 then
        milliseconds = --What would go here, I can't do 0milliseconds or 0..milliseconds
        timer.Text = tostring(minutes)..":"..tostring(seconds).."."..tostring(milliseconds)
    elseif milliseconds <= 0 then
        seconds = seconds - 1
        milliseconds = 59
    end
until minutes <= 0 and seconds <= 0 and milliseconds <= 0