Contacting a former lover to see how they’re doing is risky. Many people do it using Facebook or other social media sites. Think hard before you reach out.
The best thing that could happen is that you satisfy your curiosity. (Then what?). Other things could also occur. These might include an emotional or physical affair, which happens more often than you might imagine in this situation, disappointing news about how her life turned out, your respective spouses feeling uncomfortable about the rekindled friendship, or you feeling disappointed or rejected if she doesn’t respond like you expect or you have nothing in common anymore.
There are reasons you broke up and lost contact. Leave the past in the past if you want to remain happily married. If you have any doubts, then ask your wife for permission to contact your old lover and be ready for her questions.