How to Run Eclipse+Maven+JUnit tests in Command Line

When I run "mvn clean test", it gives me the following error: "'mvn' is not recognized as an internal or external command, operable program or batch file."

The link of my project is: https://github.com/programmingwithbangal/RestApiTesting.Framework.Leopard

I can run the tests by right-clicking on the Runner.java => Run as => JUnit Test. I can also run the tests from the JUnit 4 Test Explorer Tab.

I have read some articles where it's suggesting to set the PATH for Maven but all of them are about the case where you are installing Maven separately. I am not sure what PATH do I need to set when Maven is coming with Eclipse.

I did not install Maven separately, it came with my Eclipse version. My Eclipse Version : Eclipse IDE for Java Developers Version: 2019-03 (4.11.0) Build id: 20190314-1200