Hello student,

Well considering your category your rank for preparatory program in IITs is quite less. In preparatory course what happens is the seats remained under sc/st/PWD categories are filled. These seats are very few in number. Getting this course depends upon the number of seats available and number of candidates applying for the same

The IITs that provide preparatory program are as follows:
1. IIT Roorkee
2. IIT Kharagpur
3. IIT Guwahati
4. IIT Madras
5. IIT Varanasi
6. ISM Dhanbad

After getting a seat in preparatory program you will be taught subjects such as mathematics, physics and chemistry. At the end of semester exams will be taken and students who qualify or pass these exams will be eligible to get B.Tech courses in IITs or ISM.
You can refer the below mentioned link to know more about preparatory programs in IITs and ISM.
https://engineering.careers360.com/news/iits-announce-preparatory-course-for-scst-candidates