Lotus 1-2-3 has been discontinued long ago, but sometimes you can still find some old spreadsheets from version 3 (.wk3). If you need to convert them to Excel format (.xls), you will have to find a program that still supports Lotus formats. You can also find dedicated converters for this job, for example ABC Amber Lotus Converter, which should be capable of wk3 to xls conversion.
Open WK3 file Open XLS fileA converter for older Lotus documents