I decided to expand Mortal Kombat III Special nes rom with new backgrounds and music (from Mortal Kombat 3 (nes) and Ultimate Mortal Kombat 3 (nes)). I've checked out multiple tutorials, but I couldn't figure out how to accomplish this.

So,here's my idea:

1. https://ibb.co/album/hts38v
This is the original order of arenas in the rom.

2. https://ibb.co/album/hz738v
This is the order of arenas I planned. Arenas with 1 image should have their original music preserved. For arenas with 2 images, image on the left represents planned background and image on the right represents planned music for that arena.

3. https://gofile.io/?c=ECVDAK
This is the .rar archive which contains 3 roms - Mortal Kombat III Special for editing (target rom) and Mortal Kombat 3 / Ultimate Mortal Kombat 3 as background and music sources. Ultimate Mortal Kombat 3 can be opened with fceux.

Does anyone know how to do this? Thanks in advance.