How do you get magnet train card SoulSilver?

You can't get a Magnet Train Card in SoulSilver. That item is exclusive to Pokémon Diamond, Pearl, and Platinum.

Here's why:

* The Magnet Train is a feature introduced in Gen 4 (Diamond, Pearl, Platinum). SoulSilver is a Gen 4 game, but it's a remake of a Gen 2 game (Silver).

* The Magnet Train mechanic and the Magnet Train Card were not included in the remakes.

If you're looking for a way to travel quickly in SoulSilver, you'll have to rely on the traditional methods like flying on a Pokémon or using the bike.