The Organizational Project Management Maturity Model (OPM3) is a concept taught by the Program Management Institute.  Program Management Professional (PMP) training is covered by PMI while DAWIA training is covered by the Defense Acquisition University.  I would recommend you search the PMI repositories for an answer to this question.  OPM3 is also covered by the Federal Acquisition Institute (FAI) so you can also find information about the topic at the following link:
https://www.fai.gov/content/organizational-project-management-maturity-model-opm3%C2%AE-third-edition