ren /?
In general, commandname /?
And look up the use of wildcards on windows systems, because that is where your problem is.
ren shippingconfirmation.txt shipped.txt
Don't use wildcards if they could rename more than one file, but I'll guess from your example that you want
ren shippingconfirmation.* shipped.txt
If you don't specify the extension, windows is not going to guess for you. It will just do something weird or fail entirely.
No point in using wildcards in your situation, really. What is it saving you from typing a 3 character extension once? And as I said, you could end up renaming things you don't want renamed, as well as losing files entirely.
Like if you had
shippingconfirmation01.txt
shippingconfirmation02.txt
shippingconfirmation03.txt
shippingconfirmation01.csv
and you do
ren shippingconfirmation* shipped.txt
Guess what is going to happen? (You will be prompted for confirmation, giving you the chance to back out. But other commands which allow use of the y switch, and if used, will just let you blow stuff away with no confirmation.
Now, after all that, I'll make another suggestion and say that if you are going to REName then Move a file, you may as well learn to use Xcopy, because that is more flexible, and will let you use the /Y switch so you don't have to confirm. But then you have to DELete the original file.
xcopy C:\dir1\dir2\on order\shippingconfirmation.txt C:\dir1\dir2\fulfilled\shipped.txt
del C:\dir1\dir2\on order\shippingconfirmation.txt
If the CMD prompt is running in the original directory where shippingconfirmation.txt lives (In my example, C:\dir1\dir2\on order\shippingconfirmation.txt), then you don't need to use the full directory path to that file, just the path to the new file in the directory to which it is being moved.
Suit yourself, do it either way, whichever works best for you. You can find a full list of available commands in Help, or at the MS website, and many other places. Every command has help as well, so you can learn how to use it and any available switches it has.
Don't forget to look up wildcards (* and ?) for further usage tips that may suit your needs.