Your PC will be formatted NTFS, more than likely. Your Mac Pro will not read NTFS. You can purchase Paragon software for NTFS, this will allow your Mac to read anything from an NTFS partition. If you are attempting to move your catalog over, you are a better Man than I am, as I would not attempt that. I would just create a new catalog on the Mac.
You can also purchase MacDrive for your PC, which will allow it to read the HPS+ formatted files.
NET it's not pretty, but it will work, I do it.
Also, Mac will format a drive in a format called exFat, this is FAT32, so it will be limited to a 2 TB partition in Windows, but if you have a lot of smaller externals, this is always an option as both systems will Play well this way. BTW, Mac can read see NTFS as you can run bootcamp under a HPS+ partition, Apple just choose to not allow the Mac to work with it. Typical situation.
If you use a Drobo, this is how to make it work:
Format it HPS+ on the Mac, then use Macdrive on your PC to read it. For some reason Paragon will see a NTFS formatted Drobo, but will not load it. I have not had any problems except an occasional Blue screen on the PC with MacDrive and Drobo. Currently working with them on that.