Parameters are accessed with C4DAtom::GetParameter()/ C4DAtom::SetParameter(). See page_maxonapi_getting_started_foundations_cinema_parameters.
Parameter: N-gons
MDATA_MAKESELECT_NGONS
Parameter: Quads
MDATA_MAKESELECT_QUADS
Parameter: Tris
MDATA_MAKESELECT_TRIS
Parameter: State
MDATA_MAKESELECT_STATE
Parameter: Select
MDATA_MAKESELECT_SELECT