You don't; except in a very limited sense if you use tools that check your passwords regularly against password leaks.

But that still doesn't mean forced regular password rotation makes you safer. Changing your password is in itself a relatively high risk activity. And the likelihood of your password leaking tends to be dependent on factors you control.

For instance, if you assume that a given service provider won't leak their password database (which is usually hashed in some way), you are being optimistic. You should always expect that this can happen and act accordingly when choosing, or preferably generating, a new password.