Hello Andres,
I also could not find these strings in the Translation menu. It seems that you may have found a bug. I have filed a bug ticket here:
Hopefully the Maintainers will be able to address this in an upcoming release.
Meanwhile, in case you were not aware: local translations done via Translations bar in AtoM's user interface are unfortunately lost when upgrading - meaning the next time you upgrade AtoM, you will need to manually redo any local translations you have added. We would love to fix this in the future, but in the meantime, the best way to contribute lasting translations to the AtoM project is to add your translations to our Weblate translation interface. This way they are included in the next public release, and maintained for all.
For more information, see:
Cheers,