Once you close a sprint, it’s removed from the “Active Sprints” drop down in your Jira board. To see the issues that were resolved in a closed sprint, and to get analytics on how well the sprint went, you have to go to “Reports” and select the closed off sprint from there.
Clicking on the Reports link from your project takes you to a page with the list of reports that are available.
On that page, you will see a drop down with the list of sprints that were closed. Once you select one, you can see the issues that were resolved, or moved out from that sprint, along with a burnout chart showing how well the sprint performed.