How much is the chance of doing the AOS from F-1 to J-1 Clinical for International Medical Graduates within 3 month period because I have only 3 months. Can you answer please?

Sorry, there is no way to provide you with a numerical answer to your question with the little information that we have here.

Meet with an attorney and maybe he/she can give you a better than 50%, or less than 50% answer .... which is probably the best anyone can provide.