i have important information on my external harddrive, it has been working without a problem until yesterday morning. I tried to acces it and a message box pops up with a message ״you need to format disk before you use it" I don't Want to format it and loose the information on my harddrive. How can I recover the data on my external 1 TB verbatim external hardrive.
Don't format it, the data is still very likely all there.
First I would go into Windows disk management and see what information it has on the drive, and if possible assign it a drive letter, or change its drive letter. Next I would run CHKDSK on it, then I would check to see if security permissions have changed on the drive (right click on the drive and select properties and security tab, add Everyone to the user list), if those things fail then I would start looking at file recovery with Recuva or something similar.
HERE is a reasonably good guide to fixing the issue.
And once you do get your files back, you should back them up by something more reliable than just an external drive if they are real important. While I probably overkill backup, I would put them on optical media and a cloud backup -- there are many that are free, and I often use more than one in case one goes out of existence.