Problem with external harddrive

I have an integral external harddrive connected via usb, up until yesterday it was working fine , when you turned it on a box would appear giving different options as to what I wanted to do with the files on the drive......... now when the drive is turned on I do not get that options pop up screen.......if I go into windows explorer the drive is recognised as being there but if I click on it I get the "waiting/loading/doing something" icon then a message saying "you need to format the disk in drive h before you can use it. do you want to format it ? "

im obviously not very technical and have no idea what to do or why this sudennly stopped working.I have alot of stuff stored on this hd that I would very much like to be able to accesss again so please any help would be appreciated.
 
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