I will be traveling to Europe from California. I will be visiting Estonia, Latvia, Lithuania, Finland, and Russia (St. Petersburg). I will be bringing my UFX (old model) along with me (as part of a small rig to do some orchestral recording). The UFX has a three prong North American NEMA 5-15P plug and is marked 100V-240V AC, 50-60Hz.

What will I need to power the unit in the countries I am visiting? Will a simple plug converter work, or do I need a voltage converter? Or something else?
Any other advice would be most welcome.
Thank you.