Travelling in Finland you will meet Types C and F sockets, fed with 230 V at 50 Hz. At 230 V the supply matches what UK and European appliances expect, so no converter is needed.
You will find identical sockets in Bulgaria, Slovenia, Sweden and Bosnia and Herzegovina. Travelling further to the United Kingdom, the Isle of Man and Malta means a different adapter. Across Europe this setup is common: 31 of 50 countries.
Protective earth
Grounded and ungrounded sockets may occur
Not every socket in Finland is earthed: Type F yes, Type C no. Class I appliances belong in an earthed outlet.