Google Play doesn’t come on the Chinese ROM of the Xiaomi Mi 6 & Mi Mix 2 for legal reasons you won’t get it unless your mobile has a global or custom ROM flashed. Here’s a way to quickly get Google Play Store working on the Mi 6 with it’s new Android 7.1.1 based MIUI 8.2 ROM.
Here are the files needed to restore via MIUI backup, so you all need to do is download the Mi Pad 3 Google play files backup. Then extract and move the AllBackups folder to MIUI/Backups on your Mi 6 and restore it via additional settings, backups.
If the backup doesn’t show, it’s either not extracted or in the wrong folder!
Edit: Tested and working perfectly on the Mi Max 2 Mi Mix 2 & Xiaomi Mi 5X.