Where is super pom for maven 3?

It's documented in Sonatype's Maven reference book, which for some reason doesn't turn up easily in Google results: http://books.sonatype.com/mvnref-book/reference/index.html

For Maven 3.6.1 it's available at https://maven.apache.org/ref/3.6.1/maven-model-builder/super-pom.html

For any other version just edit the URL.

As for maven 3.5.4 in mac, it's located in

$MAVEN_HOME/lib/maven-model-builder-3.5.4.jar!/org/apache/maven/model/pom-4.0.0.xml

But you have to unzip the maven-model-builder-3.5.4.jar first, where the super pom hides.

They moved it (without documenting it as usual) to

lib/maven-model-builder-3.0.3.jar:org/apache/maven/model/pom-4.0.0.xml