.ERROR: Gradle DSL method not found: 'google()'

Question

after working on an old source code ...i upgraded everything from sdk to gradle but when i rebuilt the project i got ERROR: Gradle DSL method not found: 'google()' please help

dependencies {
    classpath 'com.android.tools.build:gradle:3.4.0'
    classpath 'com.google.gms:google-services:4.2.0'
}