Trying to get a player to change dimensions but spawn in safe location.

I've been trying to make a custom portal so that when you walk through it, it teleports you to a safe place in the overworld, kinda like the end portal. I've tried a variety of code lines but none have seemed to work. While I've used mcreator a decent bit I'm not too aquanted with some procedure blocks.

Basically I want to collide with a block in a different dimension and then I want to be teleported to (0, Safe height, 0).