How to unlock the micro sd memory card's password

Sorry. You can't. But you can usually recover use of the card by inserting it into an external SDHC card reader (using a suitable micro SDHC to SDHC adapter) and then refomatting the card. You may need to use the host computer to go into the cards properties first to uncheck the "read only" status.

This makes all data stored on the card overwriteable as if it's no longer there, but there is plenty of free/cheap data recovery software which can recover data from reformatted memory cards as long as the card has not been used after formatting.