extract password hashed in scrypt using hash and salt I have the hashed password and its salt. It is encrypted using SCRYPT by firebase.

How can I extract the plain text password from these two? 

Or alternatively, how can I re-encrypt or convert them to hash/salt that is readable by passport-local-mongoose plugin?
here is an example of what I have at my disposal:

  "hash": "jHyvk2qCPRncEAq5H05JeO4873MIMeyakVMmUXDjRfcdvflDvOXoEn7AhTW0T4f2zb24JYyPrIwTW96C4/iZ+A==",
  "salt": "zVzcUzIS+wCC+w=="
The whole point of a PBKDF like scrypt is that you can't. So that if somebody hacks the server and retrieves the hash and the salt they cannot reconstruct your password which you might have used on other sites.