Alternatively, you can also use
https://haveibeenpwned.com/They even have a notification service whereas you would be notified if one of the websites your certain email is registered on is hacked/compromised, so you can change your password on that website as soon as possible to prevent problems with your account.
Haveibeenpwned
uses cryptography to guarantee users that they don't collect their submitted plaintext passwords - but we don't know how passwords.google.com works, and if they give us any guarantees, so it's better to avoid it.
The last I checked, haveibeenpwned actually will only ask the end user to input the username/email and they will respond with any accounts associated with databases that have been compromised containing that email address or username.