Hello my name is ***** ***** certified computer professional with over 10 years experience. I will be happy to help you.
The question you are asking is impossible to answer. There is no way to cross reference every username on every website that requires a log in. Now if there is more information you think could help me help you please provide further details.
If you have no other information aside from the user name and password ***** there is no way to tell you which website it is being used on, it could be any one of thousands of websites, it is just not possible and that is a fact.
Please do me a favor and take a moment to rate my service by clicking the stars above, 3 or more is very appreciated, we can still chat after rating if you need more help.
Please let me know all the details and information about what you are trying to do and I will let you know if it is possible.