Tell me where to file my claim
or claim link
or the claim center
You're about 10 years too late... according to this story, the claim form was here:
https://www.mybitcoin.com/claim.php but that no longer exists.
The form page was never arcvhied in few web archive services i know, so i'm not sure the page ever exist. Furthermore, looks like the domain is owned by someone else now.