If you want to use Google Music you will need to upload your iTunes M4P music to Google Music.
However, Google Music only supports .mp3, .m4a, .wma, .flac and .ogg files. And DRM-ed M4P music is not supported. In order to upload M4P to Google Music, you need do a conversion first.
Since iTunes M4P music are protected by Apple's DRM, you cannot use a common audio converter to convert M4P to Google Music supported MP3. What you need is an all-in-one DRM converter that can both remove DRM protection from M4P and convert M4P to MP3 for Google Music.
Aimersoft is taken as the best choice to help you transfer iTunes M4P to Google Music. With it, you can legally strip DRM protection from M4P files and convert it to MP3. In addition, it can convert audio files that are not supported by Google Music like .wav and .aiff. Now download it and follow the steps below to convert iTunes music for Google Music.
How to convert M4P to Google Music supported MP3
Add M4P files
After downloading the DRM converter, install and launch it. The main interface is as below. You can either click the "Add..." button to add M4P music files of directly drag the files to the main interface. As you can see, you can also add video files to convert.
Specify MP3 as the output format
Then you can click "Audio files to" and select "MP3" as the output format. Note that Google Music prefer MP3 with 320kbps Bitrate. Here you can click "Settings" and choose the Bitrate as 320kbps.
Start converting M4P to Google Music MP3
When all the settings are OK, click the "Start" button on the main interface to start the conversion. When the conversion finishes, you can tap "Find Target" to access to the converted DRM-free MP3 files. Then you can upload them to Google Music as you like.
Apart from that: Why not utilize what you already have - especially if that iTunes list is big.
Here are 2 alternatives:
TuneSync™ allows you to sync your iTunes playlist and songs with your Android™ device. It copies the unprotected music to your SD card and creates playlists that match your iTunes playlists. TuneSync™ does this all over your wifi connection. There is no need to connect your Android™ device to your PC or Apple Mac.
See its home page for tutorial setup
Google Play Store Link : https://play.google.com/store/apps/details?id=com.highwindsoftware.tunesync
I think a better alternative to what you might consider is to use Winamp (for Mac):
WinAmp(for Mac) can take any existing iTunes playlist (which is what you already have) and sync it directly to an Android device without jumping through any other hoops.
Wireless and wired sync with an Android phone, requires Winamp for Android
One-click music and playlist import from iTunes and Mac desktop
Keep Winamp updated automatically with Watch Folders and iTunes library sync
Play local files, create playlists, and manage playback with a play queue window
Download and install Winamp (link depending on PC or Mac)
Launch Winamp and you'll be prompted to add media to Winamp library. Select "Import from iTunes". This will import all of your music in your iTunes library into the Winamp Media Library.
Click "Library-> Import iTunes Media Library" in the bottom left-hand corner of the player.
Sync the playlist to your Android phone connected to Mac or PC previously.
Other than serving as an easy way to sync iTunes to Android, it also makes for a decent desktop music player.