When upgrading from one 3.x version to another, please use the General Upgrade Process. This consists primarily of making sure you've got everything backed up and then just replacing your /wire/ directory with the one from the newest version.
In addition, if you are currently running any 3.x version prior to 3.0.135, you will also want to upgrade your root .htaccess file to the newest version, per the instructions below.
If you haven't made any custom modifications to your .htaccess file then you can simply replace the old one with the new one. The new one is in a file named
htaccess.txtso you'll rename it to
.htaccessafter removing your old one (all in the same directory as this README file).
If your .htaccess file does have custom modifications, you know what they are, and are comfortable applying them to the new one — go ahead and follow the step above and then make those same modifications to the new .htaccess file.
If you aren't sure what custom modifications your .htaccess file might have, or how to apply them to the new one, please see how to upgrade an existing .htaccess file.
If you are curious what's new in this latest .htaccess file version, please see this post for all the details.