Report Length
Number of pages depends on topic and the Prof. Mine has amounted to about 165 with 6 pages of references and a very large amount of research data in appendices. The actual report is around 110 pages - Calibri 12, line spacing 1.2. Larger left than right margin. Graphs, charts and diagrams are included. So your report length will be determined by prescribed layout as well as content and Prof's endurance for reading! Will differ based on many factors.
Topic
You have to look through a list of topics and apply to that Prof./supervisor. I was well-advised last year:
First choose our supervisor
Then choose your topic based on passion and interests
Good luck - it's a lot of hard work but really rewarding, opening doors to Masters study.