For PMP exam preparation, you need at least 2-3 Months. However, it depends on how much time individuals dedicate to studying for the PMP exam and how many practice exams they take. It is also important that you are using appropriate and valid study material/resources to start preparing.
If you want guidance on How to Prepare for the PMP® Exam, then it is important to get PMP Exam Preparation Tips & Tricks.