You need to research the cat command some more however I will try to help. * is a wildcard for as many chars after it as the compter can find. so....
cat /root/pass* >> newfile.txt will add every file begining in pass and ending in whatever the computer can find.
So.... based on that information you can use wild cards to merge your files.
cat /root/*/*/*.* >> onebigfile.txt will merge every thing 3 directories down from root.
once your big file is made you can sort it by alphabet and remove duplicates with cat as well
cat onebigfile.txt | sort |uniq >> bigsortedfile.txt
note the >> adds to a existing file and the > overwrites the old contents with new contents.