How to search episodes for specific podcasts using podcast api?

Use GET /search with the "ocid" parameter.

The "ocid" parameter is a comma-delimited string of podcast ids (up to 5 podcasts) - you can get a podcast id from the **podcast_id** field in response. This parameter is to limit search results from only a few specific podcasts.

It's equivalent to clicking on the "filter" link on Listen Notes website's search results:

If you haven't used Listen Notes Podcast API yet, get API keys here -  Get API keys