@tsocial241
Before doing this please check the current type of partition table.
@ernie-07
If you create a new empty partition table it will wipe out the existing partitions and Tom said he wants to keep the existing ntfs partition on that drive.
It seems likely that the drive is actually created with an MBR partition table as noted but changing that partitioning will require a backup of the ntfs data then create the gpt partitioning as well as restoring the ntfs data.
To verify the actual type of partition table in use the command sudo fdisk -l will provide that information.