* Dragonite evolves from Dragonair, which evolves from Dratini. You can find Dratini in Lake of Rage (only after defeating the Elite Four and becoming the champion).
* Dratini evolves into Dragonair at level 30.
* Dragonair evolves into Dragonite at level 55.
Since you can't trade between Pokemon Silver and Gold, you'll need to either:
1. Trade a Dragonite from another game: This is the easiest option if you have access to another Pokemon game where you can catch and evolve Dragonite.
2. Transfer a Dragonite from Pokemon Bank: This method requires a Pokemon Bank account and requires you to have a Dragonite in a game that is compatible with Pokemon Bank.
Important: In Pokemon Silver, Dratini is extremely rare, so it may take a lot of patience and luck to find one!