The Paris metro area (Aire d'attraction des villes) is only ~7,300 square miles, with the city proper only being 41 square miles. They're talking 31,400 square miles of essentially Paris proper.

So imagine the city of Paris, but stretched about 766x. If you want to include the whole metro area, then ~4.3x

Hong Kong is ~431 square miles. So about 73 Hong Kongs. But not really, because only ~25% of that area is actually urban. So more like 291x the urban area of HK.