I self plagiarized most of my work I submitted my final assignment on SafeAssign with 67% plagiarized and I plagiarized the work from me because two parts from my prievious assignment were needed to fulfill the requirements for my final assignment. Should I let my professor know or what should I do now?
Fun fact: I once read a legal paper whether self-plagiarism is right on wrong. The conclusion was: it's hard to say.

In my opinion you should let your instructor know of your concern. 

Personally, I think you should be OK, especially if the problematic assignment really depends on the previous ones. If a student approached me with this kind of problem I would rather enjoy that he has seen the connections between the problems. If you were to submit other people's work as your own, that would be problematic. However, it's always academically wise to mark the places that are based on your prior work as well.

As a personal experience: when I was studying at the uni we were once tasked with a problem and I said aloud: "Great, I can submit my solution from other class". Instructor's answer was: "The assignments that can be submitted to pass different classes are the best. I once submitted same solution to three different instructors". YMMV, but I think you'd be on the safe side if you make your instructor aware of the circumstances.