Why am I not seeing the Animoji icon in text

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

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

It is a little hard to help/advise you when you provide little to NO useful information about your iPad.

Lots of iPad year and models.

Here are my questions to you.

Can you, please, confirm what year and model iPad do you have/own?

The “A” model number can be found on the aluminium back of your iPad, in very small print, right under the larger bold print “iPad” on the back of the iPad.

AND/OR

Supply the “M” model number, which can be found in the Settings app, under the General settings panel, then tap About.

What iOS/iPadOS version is this iPad, currently, running?