I need list of ids from list of project and want to check it against project id in query

My pleasure. If you’re just starting out with Elixir I would recommend a few learning resources to dig into before getting too far with your project. I think you’ll go farther quicker if you take the time on standard Elixir first:

The official getting started guide is very good and IMO should be done from start to finish by anyone new to Elixir

The documentation on the Enum module will teach you to read Elixir documentation, and this is maybe the most important module in the standard library for programming with Elixir’s functional paradigm

Exercism.io will help you practice solving different problems in Elixir