fre:ac

free audio converter

It is completely free and open source software. 
There is support for batch conversion, preserving multiple file and folder structures. 
It supports many formats such as MP3, M4A/AAC, FLAC, WMA, OGG, etc. 
It may not have a Turkish interface, but it is relatively easy to use.
Tip: Before converting a large audio library, it's a good idea to test it on a small folder (backup the original files as well).