memory card corruption after formating

[Neui]

You may used "CGI Folder" (See Config -> GameCube -> Device Settings -> Slot A) and they are stored in GC/<REGION eg EUR>/<CARD eg Card A>/*.cgi.
Also, the .RAW-files are usually stored in GC/*.raw...

If those files are there, just copy with the same folder structure and set Dolphin to use the "CGI Folder"-Setting.