From one of your (the OP's) comments :
[T]he contract [...] states that the goal of the internship is educational. Which it was until now. Im currently implementing my research. This research includes proofs of concepts and documentation of which i graduated. but now im building an application that is based on my research
Without knowing the specifics of what you are working on, etc., it seems to me that implementing one's research, by building an application based on it, would fall under the umbrella of things that are considered educational. Especially if it is only for the few weeks between you graduating and the end of your formal internship.
Again, without knowing specifics, assuming you are a university student with limited professional software development experience, the "implementation" that you are undertaking is more for your benefit than theirs. Plenty (the vast majority) of student internships involve nothing related to research, they are opportunities for students coming from university to learn some of the skills necessary to succeed as professional software developers.
I do think you should inquire with your manager (or the internship director, or whomever is appropriate) to see if they are considering you for a full-time position, but you should definitely not threaten to leave immediately if they don't intend to.
Even if they do not plan to offer you full-time employment, you should complete the internship as agreed to. Think of your long term goals, and how completing these few weeks will further them - this is an opportunity to learn some things that will possibly help your employment search, and the opportunity to hopefully impress you manager enough that he/she will provide a positive reference for you. You manager might have recommendations for where you should apply, introduce you to other's looking to hire, etc.
Storm out of there in a confrontation, and you'll close some doors you might not even know existed. It's only 3 weeks.