thanks for your support. Off course I did a quick research too, before I posted my question, but the link does not work anymore. Also the post is from 2016, so I hoped Adobe already added a solution to the updates since 2016.
Try the script from kelsocartography.com (called FindReplace or the like)
I would lock at least half of them before running the script and then run those that have been replaced and run the other ones.