If you know the material document details,from SER03 get OBKNR using MBLNR MJAHR.
Using SER03-OBKNR, get SERNR from OBJK table.
If you know the material document details,from SER03 get OBKNR using MBLNR MJAHR.
Using SER03-OBKNR, get SERNR from OBJK table.