Comments inline.

> Hello again everyone,

>I want to learn which alert belongs to which packet when SNORT prints alert messages. Is there any unique parameter that identifies packets? 

Such questions are better suited to the snort-user list. You will probably catch wider audience there.

>For example, when I give a pcap file which includes more than 50.000 packets inside to SNORT, I want to see alert messages like that:

>[some alert] - Packet ID: 125
>[some alert] - Packet ID: 200
>[some alert] - Packet ID: 1456
>[some alert] - Packet ID: 23500

Which Snort version are we talking about here?

>If there not exist unique parameter for packets, how can I learn which alert belongs to which packet from alert messages ? 

By reviewing the packets via tcpdump/wireshark/tshark and correlating that to the detected rules? You can also chop your pcap to smaller chunks, which should make it easier.