I don't believe this form will help you much.
Basically the IRS isn't going to tell you where your father hid his money. Frankly, if it was hidden, he didn't tell the IRS anyway. That was the whole point of him hiding his money.
Even if the IRS had records, you would not be able to access his account since his tax records are considered confidential.
If you suspect your father had offshore accounts, your best bet is to hire a private investigator and/or attorney that has epxerience in locating such accounts. And even if you did locate the accounts, you may find it even harder to access them.