Hard Disk Monitoring

Health on the external hard drive is 9% and when I want to transfer data it says cannot read source file from disk.Can you please tell me how to fix this???

Yes, because of the high number of problems displayed in the text description (maybe weak sectors, bad sectors and so - as these result in such low health value) it is posslble that some of the files are not readable, damaged and can't be read.
Those files may be read/recovered - but usually they are damaged, as the contents of the currently unreadable sectors lost, the original file can't be retrieved (except if the file may have some error-correction method, for example some archive files have recovery record).

Generally the hard disk status can be fixed: the usability can be improved by Hard Disk Sentinel, to make the hard disk better and fix problems. Usually this results in increased health and more stable use - but this is more common with hard disk with higher health level. Personally I'd not expect too much about a hard disk with 9% health only.
Anyway, to diagnose the current situation, fix the problems, I can recommend the Disk menu -> Surface test -> Reinitialise disk surface test in Hard Disk Sentinel to repair the problems related to the sectors.
But this test performs a complete erase, so you can proceed only after backup of the readable, correct files.

Please check:
http://www.hdsentinel.com/faq.php#tests
http://www.hdsentinel.com/faq_repair_ha ... _drive.php

and (if the hard disk text description shows weak sectors):

http://www.hdsentinel.com/hard_disk_cas ... ectors.php

If you use Report menu -> Send test report to developer option, it is possible to check the actual hard disk status, verify the errors reported and advise about the best methods to improve the situation.

How to save damaged data on external hard drive???

This is not possible with Hard Disk Sentinel, but there are several tools available to copy files from damaged hard disks.
Usually this does not recover the lost part of the file, so the file may be damaged but at least copied.
For example, if the file is a video file, then the copied file can be played back but you may experience some glitches during playback.

Personally I did not yet use such tools, but some users suggested "unstoppable copier" http://www.roadkil.net/program.php?ProgramID=29
which can do that.