You can follow the same logic to get the serial numbers as well.
AFKO-AUFPL -> AFVC-AUFPL
AFVC-AUFPL/APLZL -> OPROL-AUFPL/APLZL
OPROL-OBKNR/OBZAE -> OBJK-OBKNR/OBZAE
Check the field SERNR for that.
Also check this --- via BAPI_ALM_ORDER_GET_DETAIL and reading the ET_OLIST table