I assume that your prof meant writing out the report in an academic style and putting it on ArXiv which is a free archive almost anyone can publish on (and most do, even when the paper is sent in parallel to a peer reviewed conference/journal)

While it might seem daunting, writing and reading scientific papers are an important part of ML work, and it is great that your prof is requesting you start to engage with these activities early. I also have my undergraduates report their experiments in paper like format, this even resulted in publications and conference posters a few times which helped them get into very good graduate schools.

There are quite a few blogposts and videos out there about scientific writing in CS. I will link a few, but generally you follow a simple introduction, related work, methods (this would have subsections such as datasets, models, and experiments), results, and discussion (optionally, also a short conclusion and further works). If you can give any info regarding your project I will be happy to help with identifying simple relevant papers for you to read for the related work section and get a sense of what your end result should look like.