Q: how to connect to iTunes from my iMac to new imacpro

Move your content to a new Mac - Apple Support

If you only want to transfer (manually) your iTunes data from old Mac to new Mac, this document explains how to make a backup of your iTunes folder (which contains your iTunes data) from old Mac to an external drive.  You can then use that backup iTunes folder and restore it on your new Mac.

Back up your iTunes library by copying it to an external drive - Apple Support

iTunes on your new Mac will look like iTunes on your old Mac, complete with songs and other media, plus supporting data such as playlists, play count, ratings, date added, etc.