What is the format of the solicited node multicast address ?

The Solicited Node Multicast Address consist of the first 104 bits of the address  FF02:0:0:0:0:1:FF00::/104 (FF02::1:FF00:0/104) and last24 bits of the Ipv6 address that is being resolved.  

For example, given the IPv6 Unicast address 2001:470:3d:3000:f02:c8e3:42e3:9c5f, the last24 bits are ::e3:9c5f (4 bits per hex digit). Put the104 bit prefix and the24 bit suffix together, and you get the corresponding128-bit solicited node Multicast address ff02::1:ffe3:9c5f.

ff02:0:0:0:0:1:ff00/104