Apple Thunderbolt 3 (USB-C) to Thunderbolt 2 adapter

With the Thunderbolt 3 (USB-C) to Thunderbolt 2 adapter, you can connect Thunderbolt and Thunderbolt 2 devices – such as external hard drives and Thunderbolt docks—to any Thunderbolt 3 (USB-C) port or USB 4 port on your Mac.

It also works the other way around, so you can connect new Thunderbolt 3 devices to a Mac with a Thunderbolt or Thunderbolt 2 port and macOS Sierra or later.