Ring doorbell transformer

Hi all, I’m looking to get a wired ring doorbell installed, but trying to understand if / what transformer I need to go along with a pro2 bell. In my chime box it looks as though the feed comes in directly from my consumer unit (the doorbell has is own on off on the unit) but I can’t see what voltage the (I assume) transformer takes things down to. I may also be looking at the complete wrong thing but thought I would ask here in case anyone has / had a similar setup. Photo of what I think is the current transformer? And chime attached - any help greatly appreciated!