I have own WP plugin under GPL2 license as need for WP, but now I wanna add some 3rd party code for directory listing and this code is under MIT license. What I need to do, that make all right and use this code in my plugin?
yes, you can include Expat (MIT) licensed libraries in your GPL plugin. WordPress plugin guidelines states,
Although any GPL-compatible license is acceptable, using the same license as WordPress — “GPLv2 or later” — is strongly recommended. All code, data, and images — anything stored in the plugin directory hosted on WordPress.org — must comply with the GPL or a GPL-Compatible license. Included third-party libraries, code, images, or otherwise, must be compatible.
Here is a list of licenses compatible with GPL.