You can:
https://docs.djangoproject.com/en/3.1/topics/auth/customizing/
The tricky part will most likely the password handling. Hopefully the
passwords are not stored in clear text in the database in which case you
need to figured out how they are hashed and salted.
If the passwords are in clear text, you should export the user database,
reimport them in using standard Django auth and inform all users that
their accounts are potentially compromised and they should change their
password ASAP.
The last part is not only the right thing to do, but to the best of my
knowledge also a legal requirement, at least within the EU (GDPR).
Kind regards,
Kasper Laudrup