こんにちは、Emoniさん。 There are subtle differences among 行くなら、行ったら、行けば. 行くなら is used when the possibility to do something is not so high. This could mean "If I have any chance to do something, I would ....." 行ったら is used when you just want to say "if I go there....". 行けば is used when there is a natural cause and effect relationship. 日本に行けば、友達に会えます(If I go to Japan, I can see my friends. You have friends in Japan. So when you go to Japan, you usually see them). 東京に行けば、たくさんの人がいます。（If I go to Tokyo, I will see a lot of people) 夏になれば、暑くなります（If summer comes, it gets hot.). There may be differences depending on the person, but generally speaking, the above rule will apply. You don't have to say "もし” all the time beause たら、なら、ば、have already conditional meaning. I hope this will help.