my 8g microsd card unexpectedly unmounted from my phone neither my phone and computer can read the files on it...i've got my files on it important school files...plsss i need urgent solution.

Sounds more like a defect on the card itself, so recovering files is not always possible.
On the computer, if the card is at least detected by Windows (even if no drive letter, it should be detected as storage, and visible in disk management through start > diskmgmt.msc)
You can try the free Testdisk app to try to recover files: http://www.cgsecurity.org/wiki/TestDisk
IF NOTHING IS DETECTED (besides the SD card reader), all hope is lost.

Replace the bad card with a new one then restore the files from your backups. If they are so important I'm sure you have several good backups you can restore them from. Besides that, you would never store your originals on such unreliable storage like sd cards only.

Testdisk mentioned above is used to restore mainly bad boot sectors, but not the data on bad media, for that you would need Photorec which is from the same manufacturer and looks almost the same:

http://www.cgsecurity.org/wiki/PhotoRec

Usually the linux version will work more reliably though, so I suggest you boot your PC to which you have the card reader connected to using the PCRepix LiveDVD which includes both, testdisk and photorec:

http://pcrepix.sourceforge.net

But as has already been mentioned, it will be unlikely you'll be able to recover anything.

i've tried but it seems it still cannot be detected...i guess its damaged..