Arihant publishes a book that contains the previous years’ questions of MU OET. Along with the previous year's questions, there are also some sample papers. You can follow this book for your preparation. It is quite helpful and offers insights into the examination pattern.
As MU OET is an online examination, the university doesn’t usually provide the question papers.
You will probably not find MUOET’s previous exam papers anywhere since the exam is conducted online. If you find books claiming otherwise, it is quite possible that these are all fake. In order to prepare, you can solve any easy level problems or other formula-based ones.
This is because the test primarily tests your speed. You will have a total of 200 questions to answer in about 150 minutes. When you do that math, you roughly have about 45 seconds to answer every question.
If you want to prepare then concentrate on NCERT books which will be enough. You can even try solving questions from the Arihant series once you are done with the NCERT.