How do I get part of a field?

[Square Wheels]

In a newsletter I created I want to display the price of a product in my store.

This is what one of them looks like (in the p_base_price field): {"USD":{"amount":15,"currency":"USD"}}

The price is $15.  It will always be USD, so I don't need that part, I just need to get the 15 out of that field.

Thanks