He appears to be using
https://www.bitaddress.org/ (or some clone of it)... it is opensource and free to download (they have a link at the bottom of the page).
Simply click the "wallet details" tab at the top, input the private key and click "view details" it'll show all the info...
NOTE: DO NOT put your private key into an online version of this website... download it and run it on an offline computer!
Also, check out some of TP's Bitcoin tools:
http://gobittest.appspot.com/ The "Bitcoin Address" and "Private Key" tests illustrate how you convert from one thing to another, step by step