Can you provide bit more details as to what you are trying to achieve? If you are looking for out of the box contentmodel, here is the link for your refernce:
All ootb models: https://github.com/Alfresco/alfresco-community-repo/tree/master/repository/src/main/resources/alfres...
You can also find the outofthebox content mdoel in "alfresco-repository-5.x.x.jar" file in the exploded war at this location: <ALF_INSTALL_DIR>\tomcat\webapps\alfresco\WEB-INF\lib\alfresco-repository-5.x.x.jar\alfresco\model\
Please note that, you should never make any modifications/alternations to the out of the box content-model.xml file.
To learn more checkout these posts:
[EDIT]: A useful response is already provided by @afaust
(ACSCE, AWS SAA, Azure Admin)