how to change extension of all files in a folder?

I have multiple files in a folder in below format.

“Filename1.drg.txt”

I want this to be changed to “Filename1.drg”. How can I do that in command prompt?

I tried ren *.drg.txt *.drg. It changed them to “Filename1.drg.drg”.

ren *.drg.txt *.

Will rename all files that end on .drg.txt by removing the extension. On this case, preserving .drg. Which is what you want I presume.

Try:
ren Filename1.drg* Filename1.drg

It works for me.