Real Admob Interstitial Ads Not Displaying During Testing of Android App

This is my first app, and it is all complete except for the ads. For clarification:

• I was able to get the test Interstitial ads to show up correctly, so test ads work perfectly
• I just added the payment information to my account a few hours ago
• I have received an email from Admob with my official App ID # and Ad Unit Id #
• I have browsed around the forums and have read it may take a few hours of a few days for real ads to show

My first question is what number should I put in the the Manifest file for real ads? From the documentation for testing:

Sample AdMob app ID: ca-app-pub-3940256099942544~3347511713<manifest>
    <application>
        <!-- Sample AdMob app ID: ca-app-pub-3940256099942544~3347511713 -->
        <meta-data
            android:name="com.google.android.gms.ads.APPLICATION_ID"
            android:value="ca-app-pub-xxxxxxxxxxxxxxxx~yyyyyyyyyy"/>
    </application>
</manifest>

To show a real ads, I'm confused about what to input for the value:

android:value="ca-app-pub-xxxxxxxxxxxxxxxx~yyyyyyyyyy

Example for the the xxxxxs - I have an App ID # and an Ad Unit Id#, but neither are long enough. There 16 x placeholders for the numbers. From an email from Admob:

Let's say my App ID # is: 1234567890

And Let's say my Ad Unit ID # is: 9876543210

Both are 10 digits, not 16 so I figure they are not a match. When I go to my Admob account and look at Ad settings for the Interstitial ad I setup I see the following:

Ad Unit ID: ca-app-pub-7777777777777777/5555555555

Question - should I place that ad unit ID in my Manifest for real ads? I also don't understand why the 2nd half of the Ad Unit ID differs from one that Admob emailed me.

5555555555 != 9876543210

And then in my MainActivity I had the test ad code:

InterstitialAd.load(this,"ca-app-pub-3940256099942544/1033173712", adRequest,

As best as I can surmise is that for real ads I should replace the first portion:

3940256099942544

Which is for testing with the code from Ad Unit ID # from Admob settings:

7777777777777777

And then after the forward slash replace the 1033173712 with the Ad Unit ID from the Admob email:

9876543210

I think I need to get a real ad to display in testing before I upload the app to the Play Store for review. I'm just really confused as which ID # to use and where. I can wait for the account to to be approved to show ads - but I don't know if the ID #s are incorrect and that is reason why real ads don't show. Any assistance would be really appreciated - this is the last step after 13 months of hard work! Thanks.

Use the App Id that you received (can be found on your AdMob dashboard also) in your AndroidManifest.xml instead of ca-app-pub-xxxxxxxxxxxxxxxx~yyyyyyyyyy.

Replace the "ca-app-pub-3940256099942544/1033173712" with your Ad Unit Id when loading Ads.

Note:

1. App Id contains a ~ (tilde) in it.
2. Ad Unit Id contain a / (forward slash).