To contribute further to the information already shared above, it's awesome that you shared what phone your boyfriend will use to play his music (https://www.motorola.com/we/products/moto-z-play)
As mentioned above, m3u files (extensions) are text not audio format. Without spending time on why you cannot use the m3u files, we need to concentrate on only working with your music MP3 format (or other below.)
Music formats you can play on the Moto Z Play phone:
Your phone can play many types of files: MP3, M4A, AAC, ACC+, MIDI, WAV, and
OGG Vorbis. Note: Your phone does not support any DRM protected files.
Note: For WMA files, we recommend you use an audio converter software to convert .wma to .mp3
For the time being, a Flash drive is not necessary to transfer music to your boyfriend’s phone. Take a look at this link to learn how to transfer music to the phone: https://motorola-global-en-uk.custhelp.com/app/answers/detail/a_id/77744#What_music_file_formats_can_I_play
You will find these categories in the webpage:
How do I transfer and use music files?
The solution below will provide you with information on:
Use Motorola Media Link
What music transfer tools do I need?
What music file formats can I play?
What headphones can I use?
Transfer music files from a computer to your memory card.
Transfer using USB
Transfer files to/from my computer using MAC or PC
Access and play music
Stream and Sync your music from your computer over the air.
Regarding the music playing in alphabetical order, typically most media players will indeed organize (by default) music alphabetically. We need to know what source you used to create your playlist in order to see if the playlist can be organized other than alpha. (For example Windows Media Player, iTunes) (Note: in your default Music folder in File Explorer, there is a way to sort your music other than alphabetically (-> View tab -> Sort)
Question: When you downloaded your music to the computer, was the music audio format MP3, or did you convert the music from a different format (extension?)
Take time to absorb the above information and of course we are here to continue assisting you!
P.S. I find what you are doing for your boyfriend just so loving and wonderful, give yourself a hug!)