This is not a ROM/game sharing site - https://retropie.org.uk/forum/topic/2/forum-rules.

That being said, there's a handy topic that it might be of help - https://retropie.org.uk/forum/topic/10918/where-to-legally-acquire-content-to-play-on-retropie.

@jediknight36 Use the secrets menu when you start a new game. Thats where you enter the password. no link cable required.