Where can I find the list of metadata type to extract specific exif

I'm working on a project where I need to make pdf from image and merge it. For this I use PDFBox but at some point I need to read the exif of an image like the orientation and the resolution and so I go with metadata-extractor. I didn't find any useful doc or example.

I find that I can read a specifics exif but I don't know how exactly

Here is a list : List, they list most of the tag you need ( a more complete one : here