ST_Zmflag

ST_Zmflag(geom: Geometry)

SELECT ST_Zmflag(
        ST_GeomFromWKT('LINESTRING Z(1 2 3, 4 5 6)')
)

2

SELECT ST_Zmflag(
        ST_GeomFromWKT('POINT ZM(1 2 3 4)')
)

3