The password in the config is a hash value. That's irreversable. Bad luck. Factory reset is the
only option. Easiest way: login on console using the serialnumber of the device as username and password. If you still have the config: restore it to the device using a tftp server and cli save config from tftp <IP> filename merge. Then before resting set the password with set admin passwd. Save the config with save and reset the device with reset.