Which file for restore

Hello folks,

We have database backup as per below schedule

May2--Full

May9--Cumulative or incremental backup

May15-Cumulative or incremental backup

May20-Full

Now we want to restore the database till May9. So as per my knowledge we are going to take the Full backup of May2 + the incremental backup of dated May9. But when I have contacted my UNIX team they ask me which file to restore.They want to me to specify the name of that perticuler file. Could you please guide / hint me which file they requires

Landscape:-

Database -Oracle

OS - Solaris

Let me know if you requires any further details.

Thank You.

Jitu