You'll need to fish at Dragon's Den. Not with a Old Rod though, unless you want a lot of Magikarp.
It evolves at lvl 55
55
Level 55
Level 55 into Dragonite.
to my knowledge,you cannot catch a dragonair in yellow version, but you can catch dratini in the safari zone
It evolves at level 30 into a Dragonair.
The Pokeathlon isn't in Pokemon Silver version.
Dratini can be found in Dragon's Den, level it up and evolve it.
level 30 into dragonair, then level 55 into dragonite.
You have a tiny chance to find one in Dragon's Lair.
Give it an experience Share and let another Pokemon battle for it.
If you mean pokemon silver for gbc an pokemon black for ds then you can't sorry