I got 9984 rank in advance which iit and can it be changed or not? And also I got 18000 rank in main Which nit ?

Hello student,
You have not mentioned which category you belong to. Based on your rank in JEE advanced exam, you have chances of procuring a seat in IIT's, only of you belong to the general category.
Predicting the colleges based on your rank in JEE main depends on both your category as well as your home state.
These are just predictions based on the trends of the past years. However you can go through the following link to know about the cut off's and ranks for the previous years and calculate your chances of selection
https://www.google.com/amp/s/engineering.careers360.com/articles/jee-advanced-cutoff
Good luck