I am trying to find out if my Mac OS CaTALINA VERSION 10.15.7 is 64Bit?

To pile on with Rudgear, not only is Catalina 64 bit, it is 64 bit ONLY and will not run ANY 32 bit software.

catalina is the first version of macOS which dropped support for 32bit apps

macOS have been 64bit only and run on 64bit cpus in many years now.

macOS and its predecessors have been 64-bit for 15 years now.

32-bit app compatibility with macOS High Sierra 10.13.4 and later - Apple Support