Turnitin (and iThenticate) are not designed to compare two specific papers.
You may want to try WCopyfind (open-source, Windows only) or Diff Checker (web-based) instead.
The software suggestions on this page are provided as information only.
CIT does not warranty the use of nor provide support for WCopyfind nor Diff Checker.
Please be aware that these are third-party tools with their own privacy policies.