By using Pay As You Go in azure, Will I be able to connect to PostgreSQL DB in mapping data flow which is implemented inside azure data factory.
I want to connect to an On-premise postgreSQL DB at source and then transform the data in mapping data flow, once done then again send the transform data back into On-premise PostgreSQL DB. If you see here, the options for PostgreSQL are not active. So does that mean that I need Upgrade to PAY AS YOU GO Subscription.
Have you configured a self-hosted integration runtime? You'll need that to get to any server on-premises. Then, have you configured and tested a Linked Service to the pg server? I'd start there. Finally, if you get that working, you should be able to create a pg dataset.