This tutorial will walk you through the process of downloading a paper and feedback that you have turned in to a Moodle assignment where the instructor has enabled Turnitin for the assignment and added comments to the assignment in Turnitin rather than in Moodle.
Step by Step
Navigate to your course in Moodle and click on the link to the assignment 
.
On the Assignment "Submission status" page, you should see a Turnitin "Similarity %" and to the right a "pencil" icon.
Click on the pencil icon and the Turnitin Document Viewer should load your paper.
Click on the Download arrow in the right toolbar. 
Select the download version that you wish to download.
The document will then download on your computer as a PDF. Any comments and the Similarity report will be at the end of the PDF in the GradeMark report.