HI,

TO join into IIM'S firstly you need to crack entrance exam like CAT and score very good and also get through other rounds like GDPI to enter into top IIMS  (99+)

secondly with regard to intership and placements ,as you are already highly qualified with btech and mtech degree + you also have work experience ,once you enter IIMS ,you can stand out the crowd and have better chances for good opportunities at your disposal with regard to internship and final placement

and let me also say that you are not poor in academic ,you are an avg student and if you want to get into IIMS you can ,provided you work hard to crack the CAT EXAM.

GOOD LUCK