I'm new. And have a question.

[DragonianDeity]

Hey and welcome to the palace! Try gelbooru.com enter futa (or futanari) in the search, and for adding things together like, use an underscore so (futa_gif) no parenthesis, hope this helps!

Actually you don't need the underscore at all, you can just type futa gif and another search word if you are so inclined. Danbooru is another site to try as well. MAybe even g.e-hentai.org, and try futanari gif.