How Can I Update Google Play Services To The Latest Version

So, I click on it and it takes me to the play store app which only has “open” & “unistall” options! I have tried: cleaning the cache, clearing data and unistalling it. I also went to Google Play Store > Settings > Build version(4.8.20) tapping on it and found that it said “a new version of Google Play Store will be downloaded and installed”, so I clicked on it but nothing happened! How can I fix this please!? Someone shed light on this.

Thank you.

BTW, I use an Android Motorola Triumph