Leaving this here since I didn't find a clear description for an Aternos noob (me).
For folks having issues with getting coordinates to show up on bedrock servers (Aternos), you'll want to go to the Console sidebar on the page where you start your server, and at the > prompt at the bottom of the console, type:
/gamerule showcoordinates true
and hit Enter.
If it says syntax error make sure you spelled that exactly correctly. 