SlaveMaker v3 games are saved with a .sol extension. To back up your saved games, navigate to your Macromedia Shared Objects folder. This may be found at:
Windows 7&8/Windows Vista:
C:\Documents and Settings\<UserName>\Application Data\Macromedia\Flash Player\#SharedObjects\<NumbersAndLetters>\localhost\<PathToInstallFolder>
C:\Users\SlaveMistress\AppData\Roaming\Macromedia\Flash Player\#SharedObjects\KANQV3NU\localhost\Users\SlaveMistress\Desktop\SlaveMaker 3.1.09c
C:\Documents and Settings\SlaveMistress\Application Data\Macromedia\Flash Player\#SharedObjects\KANQV3NU\localhost\Users\SlaveMistress\Desktop\SlaveMaker 3.1.09c
To save your games, simply copy this folder to another location on your computer (or on an external device). If you ever need to restore your saves, paste your saved files back into the directory. Do note that if you ever decide to move the install folder of SlaveMaker 3 (Or if the name of the folder changes), when you open up your game, it will appear as if your save files have all been lost. To fix this, simply return the SlaveMaker folder to its original location or copy your save files over from the old path to the new path. (All of this is done within the "localhost"... or something...)
Looks like in case the version gets upgraded and the save files are incompatible one could experience some problems in OSX.