I have a 6gen iPad with the most recent update but I can’t Memoji on a text…. No button

For iPad models that support Memoji, Stickers can be enabled (or disabled) from iPad settings:

Settings > General > Keyboards > [Emoji] Memoji Stickers - set to ON

memoji requires faceID these are the devices which support faceID

iPhone and iPad models that support Face ID - Apple Support

Re: "I have a 6gen iPad with the most recent update but I can’t Memoji on a text…. No button"

Seems Memoji can be used for Messages and FaceTime apps:

How to: Use Memoji on your iPhone or iPad Pro - Apple Support