Plagiarism in semester assignment
You should follow whatever your university policies say should be done when plagiarism is detected.  Typically reporting is the very first thing that must be done.  What will happen after that depends on your institution's policies.
In the US, many institutions have a discipline process that is progressive in the sense that the penalty for a first offense is small, but later offenses are penalized much more severely.
In my own experience with this, if you catch plagiarism in an early draft, you can penalize the student's grade on the draft, and then the student has a chance to produce a final product that is free of plagiarism. If the final paper still has plagiarism then you can give the student a failing grade or expel them from the degree program.
This requires checking for plagiarism at the draft stage in addition to checking the final paper.  However, if you don't do this additional checking then the student may get away with only a warning or a small grade penalty for plagiarism in a term paper.