Is this a small rear derailleurcage or a medium derailuer cage?
Count the number of teeth on low gear. If the cassette has 32 teeth on low gear, it could be either a medium or a long cage. If it has more than 32 teeth (like 34 or more) it's a long cage. As others have brought up, next time take a photo from the GEARED SIDE - like this... https://www.flickr.com/photos/114201398@N06/28969998431/
A pic from the opposite side - preferably better lit - would have made it ever so much easier to judge. It'd probably be faster for you to look it over real close for a model name, and run a search on that as it would to take a new pic and upload that. But that's your choice. Meanwhile I'd guess it's a medium cage.
Take a picture from the other side, better lit and not from an angle. Could be a long cage, but all you can see is a shadowy blob
Based on the gear ratio it looks like a long cage.
Take a photo from the opposite side next time.
No idea you have to look at the model number on the derailleur.