Hi Need2kn0w,
welcome to the Apple (user-to-user) Community.
You might want to see if these articles from Apple support help:
✽ Use Memoji on your iPhone or iPad Pro - Apple Support
In Messages app: (You need to be in a conversation to see the memoji button)
✽ Use Memoji in Messages on iPhone - Apple Support
In FaceTime app:
NB: Scroll to see "Become a Memoji" ....(needs to be during a FaceTime video call)
✽. Add camera effects in FaceTime calls on iPhone - Apple Support
If you still can't see the memoji button when in a messages conversation
Try re=starting your iPhone, and see if that restores order:
✽ How to: Restart your iPhone - Apple Support
All the best :-)