Download Converter.exe here and run.
usage: Converter.exe in.amr out.mp3 [sample_rate] in.amr : Bitstream input to decoder out.mp3 : Speech output from decoder [Hz] : Sampling rate of output signal in Hz; default: 24000
git clone https://github.com/lich0821/SilkMp3Converter.git
vcpkg install mp3lame:x86-windows-static vcpkg install mp3lame:x64-windows-static
Build and run.