Hello ajtol,
Thank you for using Apple Support Communities.
So, we understand that you are setting up a new iPad and want to use the same Apple ID as on your iPhone, but want to access the games you have been playing under a different ID. Currently it isn't possible to transfer content from one Apple ID to another. But what you can do is set up Family Sharing on the Apple ID you want to use and then invite the other Apple ID to join. This will allow you to share content between the two Apple ID's. See this support article to set this up.
Set up Family Sharing - Apple Support
Best regards.