however i dint shut it down but just turned off the power
Never ever do this with any NAS! A NAS is not like a USB-Stick but instead its like a Computer (actually it IS a Computer). If you just turn off the power you very likely lose data. Most of the time this is not a problem because only unimportant data get lost but sometimes you lose important data like the Master Boot Record or Partition Information.
If there is no data on the HDD you have to keep you can simply plugin the HDD into a computer and format it there. Any OS is fine.
If this is not a solution because you have data saved on it and don't have any backup (shame on you
) you have to plugin the HDD into a linux computer, check what's the problem (i think you destroyed the partition table) and manually repair / rebuild it.
!! There is no guarantee that you can restore anything what's on the disk !! But it is very unlikely that you lost all data.