Need to give Autogenerated ID to other tables.

I have a main page ie; Initiating request page
>In the initiating request page, we have three box layouts each boxlayout is from different interface and different datatable
Three Box layouts has:
1.Request info interface (Stored in seperate DBtable - Main table for initiation request(AutoGeneratedPrimaryKey))
2.Request type info interface (Stored in seperate DBtable)- The Auto generated Primarykey value should store for each request type row
3.RequestStock info interface (Stored in Seperate DB table)

> Submit of the interface which has all the three info details

In the Request type info(2), we can add multiple types like 1,2,3 for single request Initiation,
Same for Request Stock info(3), we can add multiple types like 1,2,3 for single request Initiation

But After submitting this page only the Auto generated ID will generate for main db table, In this case how can we add this Autogenerated it to other DB table rows(2),(3).