Hi, @Dhwani Anjirwala (Crest Data Systems Private Ltd) Welcome to the Microsoft Q&A platform, thanks for posting the question and for using Azure Services.
Unfortunately, it’s a Postgres to Postgres migration. I.e. the fact that it’s Flexible Postgres as a source doesn’t change much.
The general recommendation is to figure out data modeling first by following the steps outlined here. Once done you would want to create distributed tables on the destination Azure Cosmos DB for PostgreSQL cluster before you ingest (migrate) data.
For ingesting data, you may want to consider using Azure Data Factory.
Please let me know if you have any additional questions.