The Apple LED Cinema Display 27-inch is a Mini-DisplayPort display.
To use it with a Mac that has only Thunderbolt-3 ports like the MacBook Pro 16-in, you would need a Thunderbolt-3 to Mini DisplayPort adapter, which Apple does not make.
Using the Apple ThunderBolt-3 <--> Thunderbolt-2 adapter is an exercise in futility, as this adapter supports ONLY genuine ThunderBolt displays.
You could also use some adapters labeled USB-C (USB-C is the name of the connector, ONLY). Best results and highest quality are obtained form adapters rated for "4K".
In the US, Amazon is a source many Readers use to find the devices (adapters and cables generally separately) But Buyer Beware! Amazon search is divergent and automatically bring up items that are outside your specific search "in case you are interested in these as well". Also: check promised delivery dates carefully, as such items may ship direct from the Far East, and really will take the full three weeks estimated for delivery.