It looks like there are two options. The first is to use the paid software from Paragon Software. While it is not free, it appears to be the most compatible option going forward.
Western Digital also has a link to an older version of NTFS for Mac. Keep in mind that the new NTFS for Mac looks to be compatible with macOS 10.14 where WD’s software lists compatibility up to 10.12.
Paragon Software does say in their FAQ that you may be eligible for an upgrade from WD or Segate’s older versions of NTFS for Mac.
I’m a user of a Seagate or Western Digital device with pre-installed
NTFS for Mac. How can I get my update?
You are eligible for a special update for you current version of
Microsoft NTFS for Mac by Paragon Software. Please contact our Support
Service at firstname.lastname@example.org to reclaim your update.
Source: NTFS for Mac FAQ