Hi,
How can we write a scenario where we ram up VU’s in specific interval and use a fixed number of iterations overall or Fixed number of iteration per VU’s
Welcome to the community forum 
When you use a ramping VUs executor you can define different stages. However, those have a target VUs and the duration. Thus the iterations it runs will depend on the duration and how long each VU takes to run the VU code.
Depending on your case a ramping arrival rate might work better, as it will define target iterations. In this case it will use the necessary number of VUs to reach that rate.
I find that it usually helps to understand your goals when testing, and then try to adjust the test to achieve that.
Can you further describe the case, we can help figure it out, or see if this is a feature k6 is missing:
- Website testing, API testing,…
- Test type you are trying to run.
- Some context of why you need to limit the number of iterations per VU (or total), instead of using the stage duration or the ramping arrival rate.
Cheers!