You can tick off this task if you cannot simply be found via your name or place of residence in the major search engines or social networks.
Try to find yourself on the internet, identify the services and try to remove or change your personal data from there.
For example, use Google Alerts to be automatically informed via email as soon as your name or other personal data appears on the internet. You can also try using DMCA takedown requests to have your data removed from US websites. You can find out more about this in the links below.
Specialized agencies and data brokers collect public information or details from data leaks about you and sell them on to data brokers or intelligence agencies, for example.