Unable to convert classes into dex format. See the Console for details. Help please. Admob plus Unity Ads.

I have scowered forums in hope of finding a solution. I even ran a duplicate file search. I have no clue what to do. Here is the error. What do I need to do?

CommandInvokationFailure: Unable to convert classes into dex format.
C:/Program Files/Java/jdk1.8.0_60\bin\java.exe -Xmx2048M -Dcom.android.sdkmanager.toolsdir=“C:/Users/mshan/AppData/Local/Android/Sdk ools” -Dfile.encoding=UTF8 -jar “C:\Unity 2018\Editor\Data\PlaybackEngines\AndroidPlayer/Tools\sdktools.jar” -

On the most recent version of Unity, Ads are included in the editor. You must have downloaded the asset. So, it appears twice: in the editor and in the downloaded assets. In your Unity Editor, you need to remove the UnityAds assets under your Assets folder. Don’t forget to remove both the “UnityAds” folder and the “Plugins” folder that contains the folders Android/UnityAds.aar, iOS/UnityAds…