Programs enabling conversion of the file:
If your objective is to convert the file from WK1 to the file XLS, you can use any of the applications listed. WK1 to XLS conversion process in every program intended for this purpose (so-called converters) is very intuitive and everyone is able to manage converting a file.
However, bear in mind that the list may also include programs to support and work with the indicated extensions WK1 and XLS - and not only converters. In such a case, you need to open the source file WK1 and from the options available in the program, choose ”Save as... XLS" or "Export to XLS".