How can i read books in PRC format on a Sony Ericsson xperia x8?

i have a Sony Ericsson xperia x8 and i have some eBooks which are in PRC and the phone says unsupported file type. I want to use fb reader but how can i convert them.Thank you. What is the best program to convert. Is there an app that you do not need to download just there selection of books.