You really can’t help this. If I seem to be dismissive and uninterested in your help it’s because this is a fairly deep decades old problem coming to a head, and you’re responding to me as if I don’t know the difference between a file and an application. The files are indeed the issue here, since they were created in proprietary formats, some of which don’t migrate, the rest of which don’t migrate in tact, because the applications publishers held legal stranglehold’s on their format IP dating back to the Cold War, and either went out of business leaving nothing to migrate to, or buried their legacy filetypes in aggressive planned obsolescence schemes run amok in the 90s. ...these are not static files, or even singular applications. These large design & engineering projects are comprised of thousands of files of various types externally linked to each other between multiple applications concurrently, utilizing various types of intelligence and functionality, from parametric data shaping 3d model geometry, visualization, materials data, structural, standards compliance, BIM data, scheduling, collaboration, revision & lifecycle tracking with legal tie-ins supporting, etc etc etc. Today there are giant software applications that attempt to do all this. In the past, this required tying all this functionality together out of many small fragmented applications. Many of those software companies appeared simply to release a small application, and close down after just a few years, leaving their extremely simple, effective, and reliable applications to continue on ever since without update. Many have been replaced, many have not. When one of these old projects ends up back in court again, we all need to go in and present the original, unmodified files using the original software they were created in. We’ll keep old macs to access the projects that were built on the Mac, but since windows will continue to support ancient legacy applications indefinitely, the path forward is clear.
...and at least as critical, the Wacom 3 digitizers we use, the last pointing device with absolute coordinates and programmable 5 button mouse anyone ever made, is not being updated to 64bit, because Wacom is a derelict zombie.
This is more time describing this than I need to spend. OP, the point was, there are others in your situation and worse too. If you can’t migrate to 64bit, Catalina represents a clean break, either from your 32bit applications and your data locked in them or from the platform. As others have said, it’s as big of a deal as dropping PPC for intel was.