If you are digging in the correct location, you should find Silver ore beneath the ground.
Once you’re in the Mountain biome, equip the Wishbone and watch as the green particle effect begins pulse from your character.
If you’re still struggling, do keep in mind that some of the smaller Mountain biomes will not contain Silver veins, so definitely consider checking out some of the larger biomes for more luck!
As the pulsing effect becomes stronger and the pinging noise starts to sound more rapidly, take out your pickaxe and start mining beneath the ground.