I would guess you'd need measure and integration. I think Koblitz's P-adic numbers, p-adic analysis, and zeta-functions covers this. That said, are you sure this curve encloses a finite area?
I'm not even sure what a p-adic number is. The professor handed out this sheet for us to "enjoy." It's not collected or anything. It's just for us - for fun. This was one of the questions on the sheet, and it doesn't elaborate on it at all. So I have no idea if it's a finite area.