This is not a mod you put in your mods folder, it's a replacement here is how to install :

1, Extract the .rar you just downloaded
2, Open the folder and copy the .ogg files
2, Go to your mods -> TractorMod -> assets -> audio 
3, Paste
5, It should ask to replace the files, say yes

And just like that your done ! Now go ahead and enjoy your brand new plough :D !