They may or may not be already be formatted.
EASEUS will tell you anyway. You want NTFS file system if not.
Run EASEUS Todo and select Clone disk on the home screen. Repeat for your slave HDD.
If you want to add/remove/resize partitions afterwards, use EASEUS Partition Master or Partition Wizard
Note: Full format can take hours on new HDDs.
I don't know whether to recommend a Quick Format or not if you do need to do one.
Maybe others can comment on that.