How to write an expression to extract a sub-string from a SSIS variable?

Hi

How to write an expression to extract a sub-string from a variable?

I am importing some CSV files from a directory; I need to store a specific folder name in the database. I want to write an expression to do this. How should I do?

Suppose that the full directory is:

E:\Data\Unit\test\temp\91-03\all_910331\910331\SEP\file.txt

I need to find an get the 910331 from the above mentioned directory

How should I do this?

Thanks