The ADL is the Anti-Defamation League, a group fighting and cataloguing anti-semitism and other forms of hate. Their definition of a hate group is here: https://www.adl.org/resources/glossary-term/hate-group
The SPLC, or Southern Poverty Law Center is another organization that monitors and fights hate groups. You can find their list here: https://www.splcenter.org/fighting-hate/extremist-files/groups
The CAHN is likely referring to the Crimes Against Humanity Nuremburg Project. Their list is here: https://cahnlist.org/CAHN%20List%201140922.pdf
EDIT: I was likely mistaken about the CAHN. This actually more liekly refers to the Canadian Anti-Hate Network