I don't think he meant "show the actual data," I think he meant "what leaked? My name, address, phone number, email, medical records, payment history, bank account number?"
We get a "your private data is now public" email, but knowing exactly what data turns that from a depressing statement on how much corporations value their customers' privacy into something actionable.
This information is shown on the site of the breach, as example: https://haveibeenpwned.com/Breach/BakerDistributing
Yes, I meant the actual data so you know what leaked. There is a difference between leaking a password 12345678 and leaking a password that was reused on a different site. There is a difference between leaking your actual birthday and leaking 01/01/1900. There is a difference between leaking a fake address, your previous address, and your current address.
Then feel free to browse the onion and buy data that you may be included in.
There seems to be some amount of entitlement by people in this thread to get information from a third party about what a first party to them lost.
The first party that lost your data should be the one that shows you exactly what was compromised.