Hey there, @Niket310625, and welcome to the forum. Glad to have you here.
Unfortunately, this expansion case will block access to the GPIO pins entirely if you do not modify the case design. It’s designed principally for those who do not need pin access.
We don’t have any cases for the LattePanda Sigma that would allow access to the GPIO pins. It might be worthwhile checking out a 3-D printing website like printables.com if that is a requirement for your project.