On heroku, Migrating from Sqllite3 to Postgres in Django

Question

Here is what I am trying to do

1. python manage.py dumpdata > database.json

2. Changing my setting files: from

   DATABASES = {
   
       'default': {
   
           'ENGINE': 'django.db.backends.sqlite3',
   
           'NAME': os.path.join(BASE_DIR, 'db.sqlite3'),
   
       }
   
   }
   

   to

   DATABASES = {
       'default': {
           'ENGINE': 'django.db.backends.postgresql_psycopg2',
           'NAME': 'mydatabase',
           'USER': 'myusername',
           'PASSWORD': 'mypassword',
           'HOST': '127.0.0.1',
           'PORT': '5432',
       }
   }
   

   Now I m getting an error that

Is the server running on host "127.0.0.1" and accepting TCP/IP connections on port 5432?

I have following doubts

1. Do I need to create a new database('mydatabase') for postgres. If so please point out how can I do so?
2. Do I need to create a new superuser for postgres? I have been using the same user and password that I created for sqllite3.
3. What follows when above error is fixed.