Hello @Stalin Jose Welcome to QnA forum.
If the PostgreSQL database is configured to allow connections from the private endpoint , Did you try the Sink transformation settings, specifying the connection string for your PostgreSQL database using the private endpoint?
If your initial approach of using a Self Hosted Integration Runtime (IR) proved incompatible with data flows, you can use Azure Integration Runtime (IR) instead.
- Create an Azure IR in the same region as your ADF instance and your PostgreSQL database
- Add the IP address of the Azure IR to the firewall rules of your PostgreSQL server.
- In the sink transformation settings, specify the connection string for your PostgreSQL database using the Azure IR.