With the command below you can see all the 404 errors in your apache access logs. You’ll have to change /var/log/httpd/www.example.com-access.log to the path of your log file and change 20/Oct/2016:15 to the date and hour you want to look at

grep 20/Oct/2016:15 /var/log/httpd/www.example.com-access.log | grep 404 | cut -d'"' -f2,3 | awk '$4=404{print 404" "$2" "$4}' | sort | uniq -c | sort -rg