xls to wk3 conversion was useful especially in the past when users needed to transfer data between Excel and Lotus 1-2-3, but nowadays it's pretty much obsolete conversion.
The only reason to do it nowadays, is if you need to transfer your new data to old computer that still runs Lotus 1-2-3, usually accounting software in remote areas.
You can still find tools that can save to 1-2-3 format, but the most convenient way is to look for the software on one of the abandonware websites and run it through virtual machine.
Updated: October 17, 2023