If it's a soundboard you dl'd from Cydia, they usually reside in Themes. If it's a soundboard attached to a theme, same thing, just within that theme. Within an app, see above. Usually .caf files within an app. Just dl them them with Cyberduck and convert them. Use Google or Versiontracker to find a Mac app to convert to aiff or MP3. (.caf are Mac files to begin with.)