How to convert xls to xlsx

I want to convert xls to xlsx by document, but copy files does not work.

you can try this,

try saving files using SaveAs option
try saving with .xlsx format with filename
or
try selecting .xlsx format from “save as type

Probably this is the easiest and very reliable option to convert the xls to xlsx conversion.

“C:\Program Files (x86)\Microsoft Office\Office15\excelcnv.exe” -oice “C:\in\MyFile.xls” "C:\out\MyFile.xlsx”

https://gist.github.com/Opiprog/8bb6f491578d4f23540ccd98e85288c3