The ACS does have an official exam prep book, which you can find here: https://www.amazon.com/Preparing-Your-Examination-Organic-Chemistry/dp/0970804210
As long as you do some general review work it will be fine. The test tends to ask lot of questions about different topics, but it doesn't usually go very deep on any of them. I don't know how difficult your professor is but I had an Organic 1 ACS test last semester and it was the easiest of the whole class.
ACS study guide would be my favorite. Not free but your chem department might get a good discount. I think mine was like $30 a few years ago. Highly recommended.
Found an older one but it'll get the job done:
http://www.amazon.com/Preparing-Your-Examination-Organic-Chemistry/dp/0970804210
https://www.amazon.com/Preparing-Your-Examination-Organic-Chemistry/dp/0970804210
This is the study guide book we recommend to our students.
For organic chemistry, this is the bible: https://www.amazon.com/Preparing-Your-Examination-Organic-Chemistry/dp/0970804210
It's on libgen for free.
Preparing for your ACS Examination in Organic Chemistry: The Official Guide
Here’s an Amazon link: https://www.amazon.com/Preparing-Your-Examination-Organic-Chemistry/dp/0970804210
I believe there should be one for Orgo II as well.
Likely too late to get it mailed but there is an ASC study guide for that test. https://www.amazon.com/Preparing-Your-Examination-Organic-Chemistry/dp/0970804210