How to convert RAR files to NES files

My wife bought my twins this pmp game system, and i can not get the games to show up on the game system. I downloaded some game in rar, i unpacked them with winrar then they showed up as what ever game system they belong to. Instead of rar at the end it said gba for game boy advance. The manual says it only supports nes simulator games. Is there anyway to convert these game to nes format?
Any help please.

Gameboy Advanced games cannot be converted to NES games. If your game system plays NES games, you need to download NES games.If you want NES games, you can find them here:
https://www.romulation.org/Retro/NES/What is this pmp system you are talking about?

I dont know who makes it . all it shows is pmp mp5 digital player.
Sorry i am new to this.

It seems to be just some sort of media device. You are probably running a NES emulator on it? So you need to use NES games.

ok thanks. i looked at that link are all of those nes format? are they full version game? They are not very big in size.
Thanks

NES is old. The games are very small file sizes. It just goes to show you how much things have advanced in 20 years.They are NES games, and they are full versions.

ok thanks for the help.