sharing things from iMac to Mac Pro

You might have a look at this..

Use iCloud File Sharing to share folders and files with other iCloud users - Apple Support:

https://support.apple.com/guide/mac-help/share-files-with-icloud-file-sharing-mchl91854a7a/mac

Hello, di_chapp.

If you simply wish to move a folder full of files, I suggest the easiest way is to use a USB thumb drive or external drive.

Other options are available such as file sharing on the same network, or internet sharing via DropBox or other service... kinda depends on how much and how often you want to move files. For example,

the entire Photos library could be many hundred GB in size and require lots of storage space.

How much data are you talking about?