APi Level 26 to 28

Hi ,

I am using ionic 3.
And my target api level is 26 , i want to update to 26 so that i can update my apk on play store.
Please help me .

my ionic info : -

cli packages: (C:\Users**\AppData\Roaming\npm\node_modules)

@ionic/cli-utils  : 1.19.2
ionic (Ionic CLI) : 3.20.0

global packages:

cordova (Cordova CLI) : 9.0.0 (cordova-lib@9.0.1)

local packages:

@ionic/app-scripts : 3.1.10
Cordova Platforms  : android 6.3.0 browser 5.0.3 ios 4.5.5
Ionic Framework    : ionic-angular 3.9.2

System:

Node : v8.11.3
npm  : 5.6.0
OS   : Windows 8.1

Environment Variables:

ANDROID_HOME : not set

Misc:

backend : pro 

And I tried to set in following way in config.xml file :

but after that my all url(GEt And POST) is getting null.