One easy way to find which standard delivered InfoObject to use in a transformation for a corresponding field in ECC is to look at table RSTRFIELDSH, Shadow table: Transfer Structure Fields.
Let’s say you have a field in a DataSource from ECC named BWART. Just run SE16 for table RSTRFIELDSH and enter BWART in FIELDNM –> it will return 2 possible entries in field IOBJNM, either 0OI_BWART or 0MOVETYPE.
Make sure you search in a BW system, not in an ECC system 🙂