I am getting this error in the Netbeans output console.
"D:\apache-maven-3.3.9\bin\mvn.bat"' is not recognized as an internal or external command, operable program or batch file.
To execute the mvn command you should go to the mvn bin folder if you are not set the environment path to maven home. after set the maven home path you can access wherever you want.
Here easy guild to setup maven https://www.mkyong.com/maven/how-to-install-maven-in-windows/
mvn
runs Maven, which is a build tool. Are you trying to build your project or launch it? – Tim Biegeleisen