Classic is the environment that has been taken off of Macs starting with Mac OS X 10.4.4 and later.
January 7, 2006 Apple replaced its line of PowerPC Macs using the IBM and Motorola CPU (the brain of the machine), with one using Intel. For those Macs which were prebundled with 10.4.4, or later (Tiger), they no longer supported Classic.
PowerPC Macs once upgraded to 10.5 (Leopard) or later could dual boot Mac OS 9, if they were older than the Firewire 800 PowerMac G4 but still a minimum of built-in 867 Mhz, Powerbook G4s with rear ports of the same minimum speed, early eMac 1 Ghz models, but couldn't use the Classic environment running Mac OS 9 side by side with Mac OS X. Dual booting also necessitated Mac OS 9 drivers be installed before installing Mac OS X. All pre 2006 Macs supported Classic in 10.4.11 and earlier.
After then, no Mac had built-in support for the older pre-2003 Mac OS 9 operating system. Limited support for applications existed in Cocoa Apps designed to run in both Mac OS X and Mac OS 9. And Intel Macs upgraded past 10.6.8 lost their ability to run PowerPC based Mac OS X applications.
10.15.7 is not available for any Macs that ran Classic or for that matter the Rosetta 1 which allowed PowerPC apps designed for Mac OS X.
At this point, if you are running 10.15.7, you'll need to find the 64 bit Intel Mac support for any applications you desire or drivers. Either that, or find a used or refurbished Mac, meeting the vintage described above.
http://www.macsales.com/ and http://www.dvwarehouse.com are both great resources for older Macs