I am sorry but there is no efficient way how to get password from the hashed password string. SHA2 is a hash function which is considered practically impossible to invert.
To validate user's password you need to know:
- user password (input in the logon form)
- hash algorithm (in your case it is SHA2)
- hash salt (additional string used in hash algorithm)
Based on the hash algorithm and hash salt you are able to calculate user password hash. Then you simply compare the password hash from the database with the password hash calculated from the user input. If they match the password is correct.
To sum it up you are not able to recreate the user password from its hash value even if you know hash algorithm and hash salt.