WD elements 3TB for Mac shows 2 partitions one accessible

New WD Elements 3TB external drive was reformatted for Mac (Mac OS Extended Journal). This shows 2 partitions. The accessible partition shows only 1TB. “Free Space” is 2TB but not accessible. Redoing the partition does not work. What can be done?

I’m a Windows user … hard drives over 2TB need to be GPT (GUID Partition Table) partitioned.

https://discussions.apple.com/thread/6785077

Many thanks for your reply, and your contribution is really appreciated. Under device information, Scheme, it shows as "GUID Partition Map; size 3TB. But only 1TB accessible and 2TB “free space”. I think that means the partition is GUID?