https://drive.google.com/file/d/1N2qjMhPFEVKmF9o8k9sSSnougFGDr5jN/view?usp=sharing
Download that, and bring all those assets into /userdata/retroarch/assets. When you get in Retroarch, change the theme from rgui to xmb, save the config, restart Retroarch and it should look just like that