I did not know that e107 was even still around.
I googled for their site, found it, searched on it for information about phpbb and found a link to the site of the person that is developing the phpbb plugin:
http://www.diporgos.com/p/e107bb/
it is for 3.0 and there doesn't seem to be anything for 3.1
don't know about a convertor. depends on exactly what forum software your e107 is using. there is no e107 forum software. they use plugins to create a forum using things like vanilla or phpbb etc.
robert
robert