That's a padlock, and you'll have to do some drilling to get to the pins.
It's better for you to get a cylinder, access to the pins is much easier. For some of them, you can just unscrew the top and reach the pins immediately.
I would not even try to do what you're wanting to do with that padlock.
The best thing you could do is go buy a Kwikset deadbolt. There is a removeable cap over the pin chambers on them that make adding/removing pins VERY easy.
You could have the pins changed a dozen times in a Kwikset deadbolt before you could think of changing them in that padlock.
