Hello, donmcmahon1.
Welcome to Microsoft Community!
After reading what you posted, I understand that you currently have a need to use the same keyboard on two Surface devices.
And indeed, the Surface Type Cover is able to work with the Surface Pro 7:
Learn more about Surface Keyboards and Type Covers - Microsoft Support
And one issue that is in front of us is that normally, the Surface Type Cover is not compatible with the Surface Pro 9. Since I'm not with you, I can't quickly make a determination for you. So, you will need to make sure that you are currently using a Surface Type Cover on your Surface Pro 9, and from a consumer's point of view, may not have a particularly clear understanding of the model's name of the Surface keyboard. Allow me to introduce you to it here:
The Surface Type Cover is available for the Surface Pro 7+ and earlier models. And devices after the Surface Pro 7+ use the Surface Pro Keyboard.
If you are finally sure that this is the Surface Pro Keyboard, I'm afraid it won't work perfectly with the Surface Pro 7. If it is Surface Type Cover, you can use it with Surface Pro 7 with confidence.
For the sake of rigor and to avoid unnecessary trouble, we need to confirm the current keyboard model and combine the above information to make a judgment.
I look forward to your reply here.
Best Regards.
Leo.L - Microsoft Community Support Specialist