"Dad will arrive in Russia in three hours."
Translation:Папа прилетит в Россию через три часа.
There is no way of knowing that arrive means arriving by plane in the sentence :(
What are the other possibilities (e. g. dad arrives by train, on foot (because he is hiking))? Придёт? Приедет?
Приди (on foot) Прибежать (running) Приехать (by car, bus and transports) Прилетать (by plane) Приплыть (by "water" ex. Swimming) Etc . :)
Because отец is the equivalent of "father" is far more formal than dad... The meaning is the same, the form is different
В России - it happens just in Russia(e.g.: I live in Russia; I work in Russia - both mean "в России").
В Россию - something/someone goes from abroad to Russia(e.g.: I go (from abroad) to Russia - В Россию).