32 bit data files on 64 bit Macs running Catalina or later

I just received an email from an old friend who is a graphic designer. He has upgraded to a new Mac but has many files in his portfolio that were created with 32 bit applications (including the old, 32 bit versions of Photoshop, Illustrator, Word, Excel, etc.). He is concerned that if he runs the latest version of Mac OS and moves to 64 bit applications, his old graphics files will be inaccessible. Is this a valid concern? If so, how can he convert his files?

My assumption was that the 64 bit applications themselves would be able to open the old files and convert them to the appropriate new format (as necessary). After saving in a new format, the files would probably not be accessible in 32 bit apps, but they'd be fine in the new ones. Is that correct?

Thanks!