Hi Kevin,
Reporting starts in Enterprise Edition($$), and there’s no explicit API to craft them outside of that. However, you’ll be able to pull some data to craft your own reports with the issues API. You’ll find the onboard documentation linked from your page footer.
The best way to master the API is to perform the desired action via the UI and eavesdrop to see which calls the UI made to accomplish the action.
You may also find this guide helpful.
Also, make sure you upgrade to SonarQube v9.9 LTS soon, not only to benefit from our Best LTS Ever™, but because soon we will systematically ask users to upgrade when they ask questions about earlier versions of SonarQube, which are now considered unsupported. 
HTH,
Ann