I have been unable to get this to work thus far. Here is what I did with a wild card with 8 files. Never went through though.
root@kali:/media/sf_Storage_1/Master# \egrep -Ro "[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}" /*.txt | sort -u > /list-of-Ips.txt
root@kali:/media/sf_Storage_1/Master#