Hello Roshan

It would be difficult to tell you the marks required for admission as the cutoff varies every year depending on various factors. However, AIIMS MBBS 2018 Last rank for General Category candidate was 53.
AIIMS New Delhi is one of the best medical colleges in India and you must work hard and score well for admission.
You can go through the link below and check the previous year cutoff category wise for reference

 https://medicine.careers360.com/articles/aiims-mbbs-cut-off

Good Luck!