You'll need the latest version of Final Cut Express, and it's going to be tricky. Legacy FCP writes an old version of XML files. FCP X writes the new FCPXML version. They are not compatible with each other, it's a very difficult translation to do.
There is a software utility called 7toX that will translate an FCP 6 or 7 version XML file to FCPXML for FCP X to open. I'm assuming it would handle Final Cut Express files. And I'm assuming FCE has an XML export function, too.
I've emailed Philip Hodgetts, co-author of the utility, about this and will post his reply as soon as I hear.