Lightroom 6, Install needs updated, iMac, Catalina.

[Donald5C97]

I bought this disc/software over two years ago.  Life happened.  Computer needed work. Blah blah blah.  Don't ask.  

Just now opened the box to install on new imac, running Catalina.  First thing I get is the following messggage.  Any suggestions?  

[John T Smith]

New computer will  not run old 32bit software... you need an old operating system to go with that old software