How to set apk level to 28

I want to upload my game to google play store, but whenever I try to upload my apk it gives me an error:

Upload failed

Your app currently targets API level 26 and must target at least API level 28 to ensure it is built on the 
latest APIs optimized for security and performance. Change your app's target API level to at least 28.

Is there any way to get my apk level to 28 when I try to change it in AndroidManafest.xml it just sets itself back to level 26