Hello @venkat.j and welcome to the community,
I’m not sure about my suggestion, you may have not the requirements or it may not work at all. but I think you can give it a try. I think you can use coupons to achieve what you want. create a coupon, select Can be used once by multiple customers and set Maximum Number of Uses to 200. give it to your customers and wait. the first 200 volunteers can use this code to enroll on your course. it would be a trick…
There is another way but you would have to do that manually. you can check number of enrollments in your course and hide the course when it reached your desired limitation.
you can also set a tight time limit for course enrollments, or set course enrollment fee, etc.