How do I make a roguelike upgrade system?

In my game, I have a player who shoots enemies, and when they die, they drop experience. I have the system for counting the xp and adding levels done, but I need a way to have a menu pop up when ever the player levels up, pausing the game and giving a choice of three cards. I have tried looking for a way to do this, but I could find nothing. If more info is needed, let me know.

You may find useful this tutorial from Brackeys . Let us know how it goes.