Old drive now needs to be reformatted?

I have used my Mybook 2TB essential for quite some time.  Unfortunately, now whenever I connect it to my computer I am informed I have to format it before it can be used.  I don’t want to lose my data so what do I do?  Is there a solution?  If I reformat can the data be recovered?

What OS are you using? Does the drive show in Disk Management and does it say anything like Raw or  not Initialized?