Each Eye of Ender requires 1 Blaze Powder (from Blaze Rods) and 1 Ender Pearl. Ender Pearls are dropped by Endermen, which can be found in the Overworld at night, in the Nether, or most commonly in the End. You'll need 12 Eyes of Ender to activate an End Portal, though some portals may already have a few inserted.
Minecraft
Crafting Eyes of Ender — Minecraft Guide
Craft Eyes of Ender in Minecraft for the End Portal. Combine Blaze Powder and Ender Pearls for this crucial item needed to activate the portal.