Unlike PSM1 , I couldn't find many information like mock tests or Open assessments (specifically to PSM II) available in Scrum.Org . All we know is there will be 30 questions asked with 90 mins timeline. It would be really helpful if experts in this forum share where can we find mock test or open assessments available to know what to expect during real time.
I wasn't able to find any good mock tests, although I recommend practicing the Scrum Open and Nexus Open until you're consistently getting 95-100% every time. The questions are different and more difficult, but the concepts are widely the same.
Beyond that, this article has a good sample question that's fairly accurate to the question quality. Be aware that the weighting of questions shifts, so you'll see more questions asking you to pick 2 or 3 correct answers, and less asking you to pick a single response. The PSM I wants you to "pick the right answer," while the PSM II has you "pick the best answer(s)"