Learn Russian: Где Иван? Его здесь нет.

In Russian, when you want to say that someone or something is absent, you use the word нет (meaning "is not" or "there is not") followed by the Genitive case. Since Ivan is a "he" (он), we use the Genitive form его. The sentence literally translates to "Of him here there is not."

Why is Его pronounced with a "v" sound when it is spelled with the letter г?

This is a special pronunciation rule in Russian! In the Genitive case endings of pronouns and adjectives, the letter г is pronounced like an English "v". So, его is pronounced as "ye-VO".

Doesn't нет just mean "no"? Why does it translate to "is not" here?

You are right that нет is the standard word for "no", but it is also used as a word meaning "there is not" or "is absent". Whenever нет is used to show that something or someone is missing, it forces that missing person or thing into the Genitive case.

Is the word order strictly Его здесь нет?

Russian word order is quite flexible. You could also say Здесь его нет or Его нет здесь, and they would be perfectly correct. However, putting нет at the very end of the sentence is the most common and natural way to emphasize that the person is missing.