You need the original PSP game as the foundation. Search for:
Mortal Kombat Unchained USA ISO
File size: ~1.2 GB (uncompressed).
Why this game? It’s the only PSP MK title with 6 fighters per side, Kombat Chess, and Puzzle Kombat – perfect for modding. You need the original PSP game as the foundation
Some modders have created "MK11-style" mods for Unchained. To use these: Mortal Kombat Unchained USA ISO
This will not turn the game into MK11, but it will update some character skins and HUD elements. File size: ~1
If you want the best Mortal Kombat experience on your Android phone using PPSSPP, here is the legitimate path: