i saw a gameplay video someone using glalie so where I can get snorunt?
You need to be in Shoal Cave like Octazooka said, on B3F, Low Tide. Levels range from 26-30. It has a 10% chance of appearing. Good luck!
Shoal Cave is located north of Mossdeep City on Route 125, and is the only place in Pokémon Ruby, Pokémon Sapphire, and Pokémon Emerald where wild Spheal and Snorunt can be encountered.
Shoal Cave. https://bulbapedia.bulbagarden.net/wiki/Snorunt_(Pokémon)