Game Problem: Paper Mario Thousand Year Door

I have recently downloaded the Dolphin Emulator, Paper mario thousand year door for the GameCube (ROM), and the 7-zip extraction thing and I could open the Dolphin emulator but I can't extract the game/Rom for some reason and I accidentally opened it up with 7-zip and I think that is the reason why I can't extract the game/rom, can you guys help me?

No something is not adding up here? First start with the rom extension, I assume this is a 7z file or gcm/iso ? Once you give us that we can help you.

Okay so I did it and all I got to extract it but when I try to extract it from the Winrar it says that "No archive found" any tips, clues, advice?