Victoria,
The following will move files dropped on a Desktop drop folder to your iCloud Drive location. In this example, I have created an arbitrarily named new folder on iCloud Drive as Dropped. The Automator Folder Action will also pop a dialog box when done informing that it was done, and the count of files moved. Tested on Mojave 10.14.6 (18G3020), and on Catalina 10.15.3 (19D76). The folder action setup will already be completed when you save the Automator folder action.
#!/bin/zsh
typeset -ig cnt=0
ICLOUD="${HOME}/Library/Mobile Documents/com~apple~CloudDocs/Dropped"
for f in "$@"
do
OUT="${f:a:t}"
/bin/mv -f "${f:a:h}/${OUT}" "${ICLOUD}/${OUT}"
$((cnt++))
done
/usr/bin/osascript -e "display dialog \"Drop operation complete\" & return & \"Files moved: \" & \"$cnt\" with title \"Folder Action Drop Status\""

So, In Automator, you create the folder action and aim it at the designated drop folder on your Desktop. You need a single action in your workflow which is Utilities : Run Shell Script, where you specify Shell: as /bin/zsh, and Pass input: as arguments. You replace the boilerplate content in that Run Shell Script action with the above zsh script code, and save the folder action. I called mine Drop to iCloud Folder.
When done:
