1) Now , first it should it only search for files starting with FILE_* in descending order and take the file with lowest number i.e FILE_201507.list .
2) (a)Then , corresponding to that file number , it should take other files which has same number in their prefix i.e (abc_201507.txt, def_201507.txt) and change their file name and copying it to a different folder Y.
OR
(b) It should open that .list file which is having few *.csv file names that are in same X folder . it should select those files and then rename them and copy it to a different folder Y .