What’s the model number? Then look it up and see if you can find the update on WD’s support site.
Check this out and see if you need it.
Western Digital Product Software Downloads
More precisely. . . .the operating system got nuked. . . .and you are seeing the “O/S recovery screen”. Basically, the system fall back in the event the O/S gets catastrophically corrupted.
Not sure what happened. . . .need a bit more context here. . . .(i.e. what was the cause of the O/S system death?). . . but there is a “cure”.
The cure is simply to take a copy of the O/S software from the WD website (i.e. latest O/S update) and load it into the machine at the prompt. Viola. You should be up and running. You may have to “restore” (i.e. reconfigure) network and other setup options.
Of course. . .it would be nice to know how you GOT HERE. . .but. . . .