First thing to say, I do not believe this is the right place to ask for help in regards to techcology, as this is a central for League of Legends and its wikia. However, for the time being, let me offer a little help.
If you do not know what is an amr file, it is an audio file specifically for speech. Thus, it is typically lacking in quality (primarilly used by phones) and not entirely supported by major music players such as Window Media Player. However, certain audio editors, such as as Audacity, will be able to open it, thus you can make an attempt at converting it through that program (place the file into the program, then save it as a new file of your desire, such as a wav file or mp3 file), which is free. I do not recommend using converters directly through the net, as that is not as safe than actual converter programs.
I would offer more advice, such as other methods of converters, but I recommend that you first find someone or somewhere near you who knows about such items. For the former, there might be someone among your friends or family who is aware of these items; if there isn't, try to reach out to friends then resorting to post the question on a forum where the question is varely relatable to. For the latter, find out where is your nearest computer tech store or the closest online contacti for technology.