You have two options when it comes to this.
First option being download the UMRV (Build your own farm) edition. Honestly this is the best and easiest way to make your own farms on this map, however all of the farms will be blank, so if you want to keep the others as they are in the original map for detail sake, then use the second option.
Second option is to learn how to use giants editor to remove the buildings you do not want on the farm you're using. You will also need to understand how to find and remove stuff in the placables.xml if you intend to remove any of the animal pens or straw blowers.