Reference: How to Extract Sims with SimPE
These are just the notes I used when I was learning how to do this. I followed the tutorial on Mod The Sims Wiki.
Go to TOOLS in the Top Menu. Choose Neighborhood in the menu
Click Neighborhood Browser
Choose your neighborhood.
Go back up to Tools/Neighborhood
Choose Sim Surgery
Find your Sim. On the right side choose use under the top square box.
Once you do that, the word Export appears above that same box where your Sims’ picture should now be in blue.