That's extortion and illegal. Get proof and nail her to the wall

Also if she’s opened confidential mail she can get her for that too

You ought to send Bruce Willis, Arnold Schwarzenegger, Sylvester Stallone and Megan Fox to invade your ex-wife's house to exfiltrate your passport. They'd go heavily armed with a camera crew filming and they'd wise-crack as they are mowing down everyone in sight. Isn't this an obvious solution? Well, you're welcome in advance.

Get the police involved

take the police with you. she'll have to give it to them.

Officially, passports are Government Property and if they are not in the possession of the person to whom it is issued, the holder is working on some serious charges. Here in the U.S. that can include terrorism related offenses.

Call the police and report the stolen property

That's illegal but why would they have her address? If you move change the address with postal service and any others you need to right away.