wk4 to excel conversion is often searched by users looking for a way to convert old Lotus 1-2-3 spreadsheets (in case of .wk4 files from version 4) to modern, MS Excel format. Some versions of Excel still might support .wk4 directly, for the latest versions you probably have to use the import wizard and define how data in the .wk4 file are saved before you can import them to Excel.
An open-source software called Gnumeric supposedly still can open ancient formats, including .wk4 files. In the past some dedicated Lotus 1-2-3 converters were available, but most have been discontinued or removed years ago.