petrhick,
The PB3400 supports a maximum of OS 9.1. If interested, download 'OS9 Forever'; this allows you to install 9.2.x on unsupported machines. Please read how this utility works before proceeding.
http://www.os9forever.com/os9helper.html
However, if you have major problems with your currently installed OS, updating to 9.2.x may not correct them or might even compound your problems. The safest approach is to have a bootable, supported version of the OS on CD. The 3400 ran a special version of OS 7.6/7.6.1, so you would want a retail disk containing MacOS 8.0 > 9.1. If you want to run 9.x, you can buy a MacOS 9.0 CD, then freely update to 9.1. Don't buy any machine-specific CDs that have names like Power Mac of iMac on the label; you want the retail disks that support all models.