If you don't need to "find" the files it's just
grep -lF specific-string ...list-of-files-and-or-file-patterns...
or if you have to find the files
find ...file-properties... | xargs grep -lF specific-string
It it's not a "specific string" but a regular expression pattern that
you want to match in the files then omit grep's F option, use just -l.
If filenames contain blanks and whatnot, add option -print0 to find
and -0 (this is a 'dash zero') to xargs.
Alternatively you may also use find's -exec option instead of xargs.
Janis