If you have an SSA contract with Graphisoft, you can send the files to them for conversion.
If you don't have an SSA contract, you would have to run the converter on a pretty old Mac (needs QuickTime and other 32 bit stuff). In my case I installed it in a 64 bit Windows 10 virtual machine (on my Mac) and it runs fine there should I need it. If you have access to any kind of Windows computer, that might be an easy option.
One of the forum moderators • AC 26 USA and earlier • macOS Ventura 13.2.1, iMac Pro 10-Core, Radeon Pro Vega 64