Use iMac as second monitor with MacBook Pro 2020
I have a MacBook Pro 2020 (macOS Catalina) and want to use my older iMac (2011, macOS Sierra) as a second Monitor. I've connected the two devices with a Thunderbolt cable and Thunderbolt 3 (USB-C) to Thunderbolt 2 adapter (to connect it to my MacBook). When I press cmd + F2 (or cmd + FN + F2) nothing happens, also the monitor isn't recognized when I go to my monitor settings. Any advice?
MacBook Pro