I need help badly with a teleport system

So I'm trying to make a teleportation system that works like this:

You open a GUI by pressing a keybind

The GUI has a few elements:

• X Coordinate input window
   
• Y Coordinate input window
   
• Z Coordinate input window
   
• "Travel" button that teleports you to the coordinates you picked previously.
   

I have attempted this many times previously using a few methods with variables however this never seems to work and the game keeps crashing when I open the GUI.

Has anyone ever made such a thing and managed to make it functional?

Please help me.