How can we rename all files in a folder having no extension at all to “.something”.
I have tried ren *.* *.jpeg and few more but nothing working

* matches any extension. You want to match no extension, so don’t supply one: ren *. *.jpeg.

The above only works in cmd — PowerShell’s wildcards work differently, and mostly don’t do anything special with extensions. What’s more, batch renaming in PowerShell works differently. So: