Sync dependent JSON models

I have a CRM system that provides lots of functionality and contains leads, lists etc. and an internal book of record system that acts as an archive for all relationships and interactions across many systems. The CRM is current, broad in its functionality but limited in what it can represent, whereas the book of record system is limited in functionality but can represent anything.

GIven both implement query and update by JSON, I’m thinking to periodically both systems and use the JSON to update the book of record system with whatever is missing.

Postman can query them without problem. But in what should I sync the models?
e.g. I could use a script on the collections of the CRM, and somehow construct a payload for the book of record. I see GraphQL . I see newman.

But maybe Postman isn’t the way to do this.

Questions and Recommendations appreciated.
Thanks, Martin.