When you want to check similarity and AI scores on any piece of writing, you will need to use a reliable plagiarism and AI detector that is used by most universities online. Here is why you will need the access to a turnitin class with an assignment section.
Your instructor should give you access to this class by sharing with you a class ID and enrollment key. Alternatively, you can be directly enrolled in a class by sharing your email address.
However, you should be careful when you submit your work, as the submission can be done just once, or worst of all it can be repository. Repository set class means that you work will be stored in the Turnitin database and it can keep always showing as 100% plagiarized upon subsequent submissions and checks.
The work you spent a lot of time on, the last thing you would like to do is to submit it to class for a free check. You should never do that as you will later regret it.