You can set Turnitin to accept any file type in Settings > Optional Settings.

However, please be aware that the different file types have limitations with Turnitin functionality. 

For example, Excel files can be uploaded, but Turnitin only compares visible text. It does not look at formulas or hidden columns and will likely not display properly in Feedback Studio when you go to mark it. Excel files must be made using Microsoft Excel and not a third-party program that can save in the. XLSX format. Libre Office, Open Office, and others are not compatible with Turnitin and will not be accepted.  

Turnitin will not accept the following to generate Similarity Reports:

• Password-protected files
• Microsoft® Works (.wps) files
• Microsoft Word 2007 macros-enabled .docm files
• OpenOffice Text (.odt) files created and downloaded from Google Docs online
• Document (.doc) files created using OpenOffice, as they are not 100% Microsoft Word equivalent
• Apple Pages
• Spreadsheets created outside of Microsoft Excel (i.e. .ods)
• Text with visual effects

Read more here on Turnitin.com