after change level to K, it asking for format, I dont want format as i've important data, how I can read without formating

Hey there, Laxminarayan.
I guess you mean that you've changed the letter of the drive to K? Would you please give a bit more info on the issue? What is the HDD - external or internal? Do you hear any unusual sounds/noises coming from the drive? What OS are you using?

Basically what I can give you as advice now is this: try the drive with a different computer to see if the same thing happens, try it with a different USB cable (not longer than 12") and a different USB port (2.0 or 3.0) if it is an external drive and different SATA cable and SATA ports if it's internal.
For data recovery you could try accessing the drive via Linux Live CD/USB or some of the data recovery programs listed in this thread here: http://www.tomshardware.co.uk/forum/id-1644496/lost-data-recovery.html

Hope that helps.
Boogieman_WD