You want to scan SharePoint in CloudSOC integrated with Data Loss Prevention
Component: Data Loss Prevention Cloud Detection Service for REST, CASB
In order to scan SharePoint in CloudSOC with DLP Cloud Detection Service for REST:
step 1: On DLP Enforce console save a policy (policy -> policy group -> "application inspection configuration") as per steps provided in article Managing Application Detection
step 2: On CloudSOC Elastica console initiate rescan under Securlet > Office 365 > Scan
Note: it will look at all exposed docs - not just sites - for the rescan.
You may want to review: Office 365 Securlet Re-Scan