.pdf thumbnails (previews)

how do I enable .pdf (and if possible .cbr/.cbz) thumbnails?
I’ve ran this “snap run nextcloud.occ preview:generate-all -vvv” but get this error:

[Symfony\ Component \Console Exception\ CommandNotFoundException]
Command “preview generate-all” is not defined.

with some exception trace that follows.

Thanks for all the help!

I guess it is part of this app: Preview Generator - Apps - App Store - Nextcloud

That was it, didn’t realize it required an add-on! thanks again!