Most universities pay for Turnitin. Before looking for cracks, ask your lecturer or IT department if the university offers a "Draft Coach" feature or a specific portal where students can check their own drafts before the final submission.
You do not need to risk your degree. Here are legitimate ways to check your similarity and improve your writing without touching cracked software. turnitin kuyhaa
If you are a graduate student or researcher, you can use iThenticate (Turnitin's sister product for publishers). Most universities pay for Turnitin