VoltageRussia uses 220 volt electric plugs. Most of electric devices these days support from 110 to 240 volts and you can easily confirm this by looking at the electric adapter of your electronic device. If your device only supports 110 volts you will need to buy a special adapter. If it supports 220 volts then you just need an outlet adapter.
OutletsRussia uses European outlets with two round pins. You can find an adapter at any electronics and even pharmacy store in US or online.
Tip: there are no hair dryers on the cruises and if you bring your own, you should make sure that it supports Russian voltage and that you have an outlet adapter.