Parameters are accessed with C4DAtom::GetParameter()/ C4DAtom::SetParameter(). See Parameter IDs.
Parameter: Matrix
GV_MATRIX2VECT_INPUT
Parameter: Offset
GV_MATRIX2VECT_OUTPUT0
Parameter: V1
GV_MATRIX2VECT_OUTPUT1
Parameter: V2
GV_MATRIX2VECT_OUTPUT2
Parameter: V3
GV_MATRIX2VECT_OUTPUT3