How to trigger a Jenkins pipeline only when a pull request is made from a specific branch in GitHub?

Our team changed the branching strategy and that requires me to change the Jenkins settings. There is a main "master" branch and a "dev" branch.

The devs will make their individual discrete pull requests (PRs) to the dev which will trigger some unit tests on GitHub Actions, but when a PR is made from the "dev" branch to the main "master" branch a Jenkins pipeline should be triggered.

As I have currently configured the process, the Jenkins pipeline is triggered on every single pull request, regardless of the branch but what I am trying to do is only trigger the Jenkins pipeline every time a PR is made specifically the from "dev" branch to the "master" branch.