The m2e plugin uses it's own distribution of Maven, packaged with the plugin.
In order to use Maven from command line, you need to have it installed as a standalone application. Here is an instruction explaining how to do it in Windows
Once Maven is properly installed (i.e. be sure that MAVEN_HOME, JAVA_HOME and PATH variables are set correctly): you must run mvn eclipse:eclipse from the directory containing the pom.xml.