fre:ac

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).