To be honest, the CSM from Scrum Alliance is much easier to achieve than the PSM I.
My suggestion would be to take a sample PSM I exam (offered freely through Scrum.org) to truly assess your Scrum expertise. If you can consistently reach 90-100% in the sample exam, then you are ready for the actual PSM I exam.
My strong advice is to proceed very carefully with the Scrum.org certifications. The PSM II exam is much more challenging than the PSM I exam. Best to be well-prepared than to unwisely spend money on a certification exam you are ill-prepared for.
There are many threads in the forum on the PSM I and PSM II exams. Perhaps researching through those threads would be a good starting point for you. Good luck!