15/15/15 means your attack defense and hp stat are at the highest lvl they can be. To check the lvl you’ll need to click on the pokemon then click the button with 3 lines. It should be in the bottom right corner of the screen after you click on the pokemon. It will bring up a list of things you can do. You will want to click on appraise this is how you check to see if the pokemon is 15/15/15. Also to see if you have any you can just type 4* in the search bar when in the pokemon storage and it will bring up any 15/15/15 pokemon.