In Disk Management on the right-hand side there are two panes, Upper and Lower. Each of them Scrolls so you can see all they have.
The Upper Right pane shows you all the storage devices Windows now has and knows how to use. The Lower Right pane shows you those same, although with a little different info, PLUS any other hardware units that Windows does not understand. Since you say, "It says that the disk is healthy but RAW", I assume you saw this in that Lower Right pane. But maybe not.
In that pane, each storage device is represented by one wide rectangular box. Within that box the left-hand end has a bit of info on the unit itself: for a HDD, you'll see a label like "Disk 1", a type like "Basic", a size like "930 GB", and a status like "Online". To the right there will be one or more rectangles each representing one Partition. In each there will be more info. (If there are NO partitions defined on this HDD, there will be only one block labelled "Unallocated Space".) The info in each Partition shows: a name for this Partition that was assigned when Formatted, like "MyDisk", a letter name like D: , a size in GB, a File System (normally "NTFS", but in this case probably "RAW"), and a status like "Healthy" or not.
You should be looking in that Lower Right pane for a big rectangle with a HDD size of about 930 GB (That's how Windows calls a 1TB unit). My guess is that it has one (maybe more, but maybe not) Partition block on the right that says its File System is RAW. That is the Partition I recommend you Delete by RIGHT-clicking on it and choosing from the mini-menu. If there are any other Partitions in THIS UNIT ONLY - NOT OTHERS!! Delete them also so that the entire HDD area is Unallocated Space. THEN right-click and choose to Initialize, etc.