The Scheme must first be transferred. I transferred it by switching to a new database and migrating.
https://dev.to/coderasha/how-to-migrate-data-from-sqlite-to-postgresql-in-django-182h
Migrate data from SQLite to PostgreSQL
Dump existing data:
python3 manage.py dumpdata > datadump.json
Change settings.py to Postgres backend. Check this awesome tutorial by Digital Ocean:
How To Use PostgreSQL with your Django Application on Ubuntu
Make sure you can connect on PostgreSQL. Then:
python3 manage.py migrate --run-syncdb
Run this on Django shell to exclude contentype data
python3 manage.py shell
>>> from django.contrib.contenttypes.models import ContentType
>>> ContentType.objects.all().delete()
>>> quit()
Finally, run following command to load the json data:
python3 manage.py loaddata datadump.json
Great! Now, your all data migrated from SQLite to PostgreSQL.
There is also interesting question on StackOverflow about MySQL vs PostgreSQL.