Nether Fortress Finder
Edition
Version
Seed
Open the fortress and press Overworld side: the map shows the matching Overworld spot. Build a portal there, and it opens close to the fortress.
On Java, fortresses and bastions share one grid in the Nether: each spot holds one or the other, chosen by the seed. Bedrock places them by its own rules, and the map follows whichever edition you pick.
On Java Edition, type /seed in chat (it needs cheats on, or operator rights on a server). On Bedrock, open the world's settings: the seed is listed under Game.