Hi there n1cholle,
To start, you'll want to be sure you're signed into iCloud and the iTunes Store with the same Apple ID you used to make the purchases. Learn how to sign in below:
Sign in on your Mac
1. Choose Apple menu > System Settings. In earlier versions of macOS, choose Apple menu > System Preferences.
2. From the sidebar, click Sign In with your Apple ID. In earlier versions of macOS, click Sign In.

4. Enter your Apple ID and password.
5. If prompted, enter the six-digit verification code sent to your trusted device or phone number and complete sign in.
You'll find those steps here: Sign in with your Apple ID - Apple Support
Next, make sure your Mac is authorized to access your purchases with the guidance here: Authorize or deauthorize your computer for iTunes Store purchases - Apple Support
Take care.