linked issues to epic with specific project ID

[antoine]

Hi, 

here is my set up:

issues are linked to epic and epics have a field "project ID" filled.

I'd like to retrieve all issues linked to epics, where the epics have the "project ID" field filled with a specif project PR-xxxx (or list of projects).

Can someone help me building the corresponding JQL query.

Many thanks for your help