after that u do some home work like @devilsadvocate and @atom recommended, if reaver and pixie dust aint working, u could use some online site which hold big wordlist and if it hits the password u will get a notification via mail and tells u what length is that, and if u wana recover it u will need to pay some money..
but first try to attack via reaver and pixie dust u might get lucky
but first try to attack via reaver and pixie dust u might get lucky