..., which is worth of about 7.1 billion dollars.
It seems that "of" is not needed.
▪ a ruby worth five million dollars
▪ This painting is worth a fortune.
▪ You should be paid what your labor is worth
▪ Each correct answer is worth five points.
▪ an actor worth several million dollars
▪ The corporation is worth billions of dollars.
Source: http://www.learnersdictionary.com/search/worth