On my iPhone, the emoji keyboard is to the right of the number keyboard:
Due to muscle memory, every time I’m typing on my iPad I bring up the emoji keyboard in error. I won’t ask anyone to explain why Apple have been inconsistent here, but is there a way to reverse them? I’ve tried removing and re-adding the emoji keyboard in settings, but that didn’t work.
I did file this as a bug during the beta testing of iOS 12, but I'm fairly sure it still remained a problem in the final release. However, my iPad is running iOS 12.1 beta and the keyboard now matches my iPhone: