Find all files with the ".txt" extension in the root directory and sort them, then use xargs to execute the command "echo mv" followed by the file path and the output of the command "mktemp -u /tmp/outputXXXXXX.txt" which creates a unique temporary file in the /tmp directory.
sort <(find /* -name "*.txt") | xargs -I {} echo mv {} $(mktemp -u /tmp/outputXXXXXX.txt)