To get emerald in survival mode in Minecraft, there are several options. In the creative mode, it is a mineral that you have available directly in the inventory.
Emerald Ore
The first option is to find an emerald ore and mine it. Where to search? In the extreme biomes, only there you can find this kind of block. For example, in Extreme Hills or any other biome with extreme hills. You have to look between layers 4 and 32, and you have to know that they are not in groups. For every emerald ore mined, you will get an emerald. You need an iron pickaxe or better, so you must have previously crafted the necessary elements to create such a tool. An enchanted pickaxe with a touch of silk will let you get the full ore.
This ore can also be melted in an oven to obtain an emerald. Simply place the ore and any fuel in the oven.
Getting an emerald with a furnaceNegotiating with villagers
The second and possibly easiest option is to get it by negotiating with the villagers. Many of the deals they propose involve this mineral, so you can trade items in your inventory such as food, wool or coal for emeralds.
Trading usually involves emeraldsFinding chests
There is a third option, which is to get them in the chests of the igloos, in the chests of the desert temples, in the temples of the jungle, and chests of the city of the End. However, the probability that you will find one in this way is very low.
Get emeralds from chestsKilling a Vindicator or Evocator
The last alternative to get emeralds in Minecraft PE is to kill a Vindicator or an Evocator. If you destroy one of these monsters, you will get an emerald.
Kill a Vindicator to get an emeraldEmerald is the rarest and most difficult mineral in the game, even rarer than diamond or gold. It will serve you mainly to trade with villagers or as a decorative element for your buildings: with 9 emeralds you can create an emerald block.