Since Pokémon Legends: Arceus is all about the single player orientation in Hisui region, there are many features removed, that once were earlier experienced by players. Trade Evolutions is amongst these inhibited features. This property allowed the players having few Pokémon to carry the procession of turning them into more powerful forms.
One example of new evolution method is Kadabra, the Psy Pokémon, it in past was practiced through trade evolutions. Kadabra is a historically known Pokémon for being capable of evolving into the most powerful Psychic-type Pokémon, Alakazam. The evolution proceeded through trading with other players. If the player who gave his Alakazam to other in exchange for Kadabra, wants it back he/she can undo the exchange trade. Though trading returned in Legends: Arceus, However this method is now not available for evolving Kadabra.
Figure : Screengrab via Nintendo/The Pokémon Company
Linking Cord Item is a new tool used for evolving kadbara into Alakazam, it looks analogous to the Link cable which players have used earlier as well to connect with their older generation Pokémon games. To get your hands on the Linking Cord exchanging trade points at the Trade Post in Jubilife Village. The process requires 1,000MP to carry out this trade. It can also be found on rare occasions in space-time distortions, though this is not confirmed.
Once kadbara is evolves into Alakazam; player will own one of the brisk and powerful Psychic-type Pokémon of the series. While Alakazam has poor defences, its expanded move pool in Legends: Arceus makes it a resourcesful addition to any provided team.