Kay Here is your Answer. Star Wars Episode 4 came out in 1977. In 1980, Episode 5 came out. Three more years later in 1983, Return of the Jedi came out. Then Wait 16 years. 1999, The Phantom Menace came out. Three more years later in 2002, The Attack of the Clones came out and in 2005, The Revenge of The Sith came out. Three more years later in 2008, The Clone Wars Came out. So the Direct answer is 3. But between the Trilogy's it was 16 years.
In-universe, Episdode VI takes place one year after Episode V, which is three years after Episode IV, which is nineteen years after Episode III, which is three years after Episode II, which is ten years after Episode I.