As a heads up: DO NOT attempt to open a cloud workshared project via desktop connector, double do not attempt this via an API method. That is an express lane to many various problems with cloud projects, as it removes any degree of worksharing if/when it actually allows you to work on the file. Bad things in all cases.
Your project and model GUIDs can be found in your Revit journals and/or collaboration cache.
Typically bulk processing of models (as it sounds like you are doing here) is best accomplish via Forge.