"Me llamo Bob" is the most informal of the three phrases. It is used in casual conversation and is equivalent to saying "I'm Bob" in English. For example, you might say "Me llamo Bob" when you are introducing yourself to someone for the first time.
"Soy Bob" is also an informal phrase, but it is slightly more formal than "Me llamo Bob". It can be used in both casual and formal settings. For example, you might say "Soy Bob" when you are speaking to a customer service representative or when you are giving a presentation.
"Mi nombre es Bob" is the most formal of the three phrases. It is used in formal settings and is equivalent to saying "My name is Bob" in English. For example, you might say "Mi nombre es Bob" when you are writing a letter or when you are speaking to a judge.
In general, you can use "Me llamo Bob" in casual conversation, "Soy Bob" in both casual and formal settings, and "Mi nombre es Bob" in formal settings.