How to automatically generate portals and link portals to them?

[Anglophobia]

Hello, when players in my server use the nether portal to the nether, they will teleport to a set spawn location. The portals are linked both ways and I have no clue on how to make them automattically generate. The players needs to be able to teleport to the other portal like in vanilla minecraft. I dont remember changing anything about these settings

[TharkNethIta]

i'm searching for same thing