There are five main part in an ARP packet:
-first 48 bits of destination address
-48 bits of source address
- type will be 16 bits
-data length can be up to 1500 byte
- and CRC check sum will be 32 bits.
Note: I don't expect people to memorize the exact byte/address format of packets! (I would provide reference materials for that). However, it is good to know what kind of information the packet headers hold, and what the point of the packets are.