macbook pro – How to remove Windows partitions on external HDD?

External HDD appears to be in 3 different volumes after erasing to MacOS Journaled

Hi! I wonder what is the correct procedure to remove all partitions from an external HDD (500GB) that was previously a Windows boot HDD (Extracted from my old PC).
Before the erase, there were 3 partitions:

  1. Win7
  2. System Reserve
  3. Data

After backing up and erasing the drives, they’re now empty.
I’d like to remove all the partitions but it doesn’t seem to allow me to delete by clicking “-” from the Volume on the 2nd top left on the Toolbars.

Any idea how do I do it?