BAPI
How to Find Bapi for Particular Transaction in SAP?
Suppose you want to find the bapi for creating a sales order, you usually use transaction VA01 for this. 

Method1. 1. Go to t-code VA01.

2.Go to system-->status.

3.Double click transaction VA01. 

4. Double click on package.

5.Read the application component. (this is SD-SLS Sales) .

6.Then open the transaction BAPI .

7.Sales and distribution-->Sales-->sales order-->createfromdat2 .

Suppose you want to find the bapi for creating a sales order, you usually use transaction VA01 for this. 

Method2.1. Go to t-code VA01.

2.Go to system-->status.

3.Double click transaction VA01. 

4. Package is VA.

5. Open this package in SE80.

  
6.Open business engineering-->Business object types
Find the BO which sounds the most appropriate
I would suggest BUS2032 Sales Order.

7. Double click. 

8. Open methods.

9. Find the released method with from data or something similar in the name
, Createfromdat2 .

10.Position the cursor in it and click the program button.Scroll down to find the bapi used in this method .