Hi Abhijeet! Eric from Mixpanel Support here. I’d follow these steps to get what you want in the report:
1.
I would select “All Events” in the query builder, and use the First Time Filter.
2.
Then, I would filter for the specific event name you want or just leave it blank if that does not matter
3.
If you are trying to see a group of people who did a certain event as their first event, I would click on the bar with that event name and “view users” to see the people who did that event as their first one.