Final answer:
The written patient's acknowledgment of the Notice of Privacy Practices should be retained by the pharmacy for six years.
Step-by-step explanation:
The written patient's acknowledgment of the Notice of Privacy Practices should be retained by the pharmacy for a period of six years. This is based on the Health Insurance Portability and Accountability Act (HIPAA) regulations, which require healthcare providers, including pharmacies, to keep patient records for a minimum of six years.