like Whappo said, a .m3u is a mp3 playlist file. Sending several songs via bluetooth can take a long time.
Does your phone have a usb connection to your pc?
As a matter of fact, are you storing the songs directly to your phone's memory, or are you using a micro SD card? If you are using the micro SD then you can put it into an SD card adapter, which should have come with it. Then you can put that into the SD card slot on your computer and copy/paste the files onto the card. I suggest make a folder titled audio or music. That would probably the easiest way.