Well, there is no convertor to do that directly. It is quite an old version of IPB that you're running.
We do have a convertor available from IPB 2.3 to phpBB 3.0
that you could try to use. Since it's not exactly the same version, it might give you some trouble, but have a look at this support topic
to solve some of these potential problems. After you've converted to phpBB 3.0, you can then upgrade to 3.1
. Good luck!