Importing and exporting save files.

So what I am trying to do is make it so my game can export save files for sharing and be imported by other players and used as their own. My problem is my save and load system only works with 3 save files. These are defined by these names buildBattles.(save number which is 1-3).bb which saves the file in binary. What I am really asking I guess is how do I list all save files with .bb at the end? And how might I allow the user to select said save files?