I can't find litematica 1.21 but this mod is updated to 1.21...
How can i run it in 1.21?

Please note that neither this mod or the Litematica mod are updated to 1.21.
The 1.21 version of this mod will have to wait for Litematica 1.21 to be released, and Litematica 1.21 will have to wait for MaLiLib 1.21 as well.

Hi, as per this reddit post

https://www.reddit.com/r/litematica/comments/1di4o3h/announcement_about_litematicas_future_and_updates/

Litematica has been ported to 1.21 : https://github.com/sakura-ryoko/litematica/releases/
and Malilib: https://github.com/sakura-ryoko/malilib/releases/

Just in case it's not known - these are now available :)

@aleksilassila any update please? :)

1.21 version added here https://github.com/aleksilassila/litematica-printer/releases/tag/v3.2.1