Sorry I missed this one.
It appears that you have drives that are formatted in a way that precludes the NAS from doing a proper Linux format. Before you can use the disks in the NAS they have to be returned to their virgin state (windows does some strange things to disk drives , especially win 10). It sounds as if win 10 has turned the drive into a GPT disk from an MBR disk.
You need to download the manufacturers disk tools and use them to restore the disks to a clean state (no partitions or data on them) then the NAS firmware should be able to format them as RAID 1 without problems, assuming you have the latest firmware on the NAS.
Getting windows near a Linux formatted disk is usually bad news for any data on the disk because windows does not understand the Ext3/4 file system.