Unfortunately, I'm not quite sure what exactly you mean by NAS firmware. If you mean the software with which this NAS runs, it does not have to be installed on the hard disks. You can buy normal hard disks without special requirements and install them in this NAS.
If the NAS is only running for a few hours at a time and is completely switched off when not in use, then in principle you can use any hard disk. If the NAS is to run 24 hours a day, 7 days a week. Hard disks that are optimised for continuous operation in NAS are recommended. These would be, for example, Seagate Ironwolf or WD Red hard drives.
Have a look at the manual for this NAS
http://products.wdc.com/library...