Are you sure you completed the setup? In <https://nim-lang.org/install_windows.html>, in the section Compiler Dependencies, it gives links to MingW for 32 and 64 bit windows. Choose the MingW version you want, download the .7z file, put the folder inside somewhere, then put the "bin" folder inside that folder into your PATH environment variable.
I noticed the Turkish in the screenshot so I can translate the answer: <https://nim-lang.org/install_windows.html> linkinde Compiler Dependencies'e inin, MingW 32 bit ya da 64 bitten seçip indirin. İçindeki klasörü bilgisayarınızda herhangi bir yere koyup o klasörün içindeki "bin" klasörünü PATH sistem değişkenine ekleyin.
