I there any unix command which will convert xls file into xlsx file?
Also i have tried using mv command, it is changing the extension as well. But then i am not able to open the xlsx file.
mv .xls .xlsx
Any suggestion will be really appreciate.
As far as I know, this is not something you can easily do with standard unix tools.
You can use LibreOffice:
libreoffice --convert-to xlsx my.xls --headless
Or maybe find an online converter and submit your file to it.