copy the folder "caveexpress" to the "exporters"-directory of TexturePacker 3.

Find more information at https://www.codeandweb.com/texturepacker/documentation#customization

example for windows: "C:\Program Files (x86)\CodeAndWeb\TexturePacker\bin\exporters"
example for linux: "/usr/share/texturepacker/exporters"
example for macos: "Applications/TexturePacker.app/Contents/Resources/exporters"

now you can chose the data format "CaveExpress" in the output options.
