Most of the Xiaomi devices are now running on Android Marshmallow based MIUI 8.
MIUI is a custom ROM on the top of stock Android operating system.
As MIUI is a custom ROM, it does not come with pure stock Android M ringtones.
This ringtone collection contains all Android Marshmallow ringtones.
Download the Android M stock ringtone collection from the above link. You’ll get a zip file. Now unzip the zip file to get all the ringtones.
There you’ll find total 12 stock ringtones.