Format converter design pattern

Dears,
I'm new to Design patterns, and I want to make have small
application that converts from a format to another & vise versa.

Converts: A modified version of ISO8583 <--> special XML tag

There is already a free component http://www.jpos.org/ but I have
modified version and some special cases so I can't use it.

I want to build this component & I was wondering if there is a known
design pattern to follow for building such module.

Any recommendations?

Thanks in advance.

.