My kid lost his base

So I know very little about Minecraft, but my 5 year old loves to play on the switch. Today he was playing in creative and went up into space, somehow got lost, and can’t find his base now. I have no idea how to help him, so here I am, Reddit.

Edit: wow, thank you all for your advice! We were able to locate his base really quickly with the compass. Thankfully it was near his original spawn point. Also appreciate the tips for keeping track of coordinates! Y’all really came through ☺️