30,000 pictures use how much space?

How big are the picture files? You can find it's size by selecting it and using the Get Info command (from the File menu or on your keyboard command + I. Even better, if you have all the photos in one folder, select the folder and use the same Get Info - you'll see the size of everything in it.

FYI, picture files come in many different formats and sizes.

Total could be as little as 1 GB or more than 300 GB or even double that.....