3
Depending on your 1.3.x version, you could perhaps upgrade by uploading the entire XOOPS 2.0.13.1 package (WITHOUT mainfile.php) and run the installer - it should detect your existing installation and ask you to upgrade.
ALWAYS DO A BACKUP OF FILES AND DATABASE PRIOR TO UPGRADING!
"When you can flatten entire cities at a whim, a tendency towards quiet reflection and seeing-things-from-the-other-fellow's-point-of-view is seldom necessary."
Cusix Software