Try using the name of the spell instead of the spellID. Failing that, copy this into chat:
Code:
/run FindSpellID("Spell", "unit")
Replace "Spell" with the name of the spell, and "unit" with the unit that the aura will be placed on. Keep the quotes. If it's a debuff, add true to the end like this:
Code:
/run FindSpellID("Spell", "unit", true)
This will output the spellID for the aura into chat.