HandyNotes

 It will add the locations and rewards for rare mobs, battle pets, treasures and other miscellaneous points of interest to the map.

https://www.curseforge.com/wow/addons/handynotes

After installing HandyNotes addon you can then add other handynotes for specific things/zones etc

https://www.curseforge.com/wow/addons/search?search=handynotes