If something went wrong you would simply go to your backup and replace any missing ones.
You do have a backup routine in place?
You will only lose data that you do not back up and, with OS X, there is no excuse to not backup. It's built into the system.
Make sure your backup is up to date and then update iPhoto.
You may also want to consider updating to 10.10
P
My mac is running on OS X version 10.9.5, and currently my iPhoto will not open its version is 9.2.1. I have read about updating iPhoto to version 9.6, but I am reading problems with loosing photos. Any suggestions?

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