How to recover flashdrive transcened 4gb v30, it can detect but i can't open?

Files on a flash drive can be corrupted if it is not removed from the USB port properly.
Before removing the flash drive click on the Safely Remove Hardware icon and then click on the flash drive you want to remove and then remove the flash drive when the computer message says it is Safe to remove.
To restore the flash drive you may need to format the flash drive, but you will lose the data stored on the flash drive.
If you need the data on the flash drive this program may help: -
Digital Photo Recovery
www.artplus.hr/adapps/eng/dpr.htm

Why you cannot open your flash drive that is detected well on your PC? Is it asking you to format and shows as RAW in Disk Management? If so, it is not too difficult to fix this flash drive and also extract your wanted flash drive data.
Merely do not rush to format this flash drive and also do not write new stuffs on this USB drive. And then, plunge it to your PC and download RAW format flash drive data recovery software to see whether you can recover desired original drive files back.
Read more here: Flash drive RAW format asking to format
Remember to format this flash drive after rescuing everything useful back and restore its functional use.

To repair transcend flash drive, you can use software from transcend service center. This software, can use to repair flash drive (RAW format, free space 0 bytes, used space 0 bytes, damage firmware, update firmware) and backup data.

JetFlash Recovery Tool (Win 2000, XP SP2, Vista, Seven)

JetFlash Online Recovery (Win 2000 SP4 & Win XP SP2)