Dear Karthik,
If you have Customer ID captured in Adobe Analytics, Visit Number will help you to understand this.
Let's say my Customer ID is ABC-123. If i have placed my order during my first and last visit(Say 5), the below table will give you the answer.
From here, you can calculate the visits between first and last order. For above case, 3.
But if you want to understand the average for the list of customers you have, you need to tag the logic to capture the same. It is not readily available!
Thank You!
Arun