There are two ways to export Sims from the Electronic Arts Sims 3 game:

• in a .sims3pack-file created in the folder My DocumentsElectronic ArtsThe Sims 3Exports when you “share sim”
• in a .sim-file created in the folder  My DocumentsElectronic ArtsThe Sims 3SavedSims “when you save sim to bin”
  

To export or to save any sim in game, take them to a mirror, select “change appearance” to load your sim into CAS, look down at the bottom of the screen at the little square portrait of your sim with the options dots in the corner, click the dots and choice the option “share sim” or “save to bin”.