Hello aspirant, hope you are doing good.

Firstly, congratulations for your preparatory rank,  this is an additional chance given to you to qualify for IIT next year, so make sure you make the best out of it. You will be trained for a year under any of the IIT , whichever you get in the counselling, and after a year, you will have to pass the exam of the college to get a confirm seat in the IIT.

Some of the IITs that provide preparatory courses are:

1.IIT Roorkee

2.IIT Delhi

3.IIT Mandi

4.IIT Guwahati

5.IIT Kharagpur

6.IIT Bhubaneshwar

7.IIT Patna

8.IIT Madras

9.IIT Bombay

10.IIT Hyderabad

You can get into any of this for your preparatory course, given you have an excellent preparatory rank, see what happens in the counselling.

If you want to know about all the possible colleges you can get into with your JEE Mains rank, you can get it here:

https://engineering.careers360.com/jee-advanced-college-predictor?icn=QnA&ici=qna_answer

Hope this helps you. Good Luck!!