Hello timosborne545,
There are a few things we would suggest to get as much data from the Mac mini to the iPad Pro.
Since they use different operating system, iCloud is going to be a convenient way to sync the data.
Using the same Apple ID on the iPad will sync everything that is iCloud enabled.
Follow the instructions found at Set up iCloud on all your devices - Apple Support to enable things like iCloud Photos, Contacts, Calendars, Messages, and any other data you want onto the iPad.
Be sure to enable iCloud Drive as this is going to be one way to move other data files. Any files moved to the iCloud Drive folder on the Mac mini will appear on the iPad. One thing to keep in mind, files that open on the Mac version of an app may or may not be able to be opened on the iPad. It will depend on the file and the app.
You can also use these steps found at Transfer files between iPad and your computer - Apple Support:
1. Connect iPad to your Mac.
You can connect using USB, or if you set up Wi-Fi syncing, you can use a Wi-Fi connection.
2. In the Finder sidebar on your Mac, select your iPad.
Note: To use the Finder to transfer files, macOS 10.15 or later is required. With earlier versions of macOS, use iTunes to transfer files.
3. At the top of the Finder window, click Files, then do one of the following:
• Transfer from Mac to iPad: Drag a file or a selection of files from a Finder window onto an app name in the list.
• Transfer from iPad to Mac: Click the disclosure triangle beside an app name to see its files on your iPad, then drag a file to a Finder window.
To delete a file from iPad, select it below an app name, press Command-Delete, then click Delete.
Cheers.