|If the batch file is put in the same folder as the file, it's:|
Ren "OMG0 3611 400 1011102.pdf" 1011102.pdf
The quotes are important around the first file because it contains spaces and is longer than 8 characters.
You have to specify the full path if the batch file is to be run from elsewhere.
Out of curiosity, why do you want to do this from Command Prompt?
Always pop back and let us know the outcome - thanks