Final answer:
Eliza's grandpa has these memories stored in his long-term memory.
Step-by-step explanation:
Eliza's grandfather would have his memories stored in his long-term memory. Long-term memory is the part of our memory system where we store memories that we consciously try to remember, recall, and report. It holds information that has been encoded from our short-term memory and can be accessed later when needed. In the case of Eliza's grandfather, the memory of meeting her grandmother 50 years ago would be stored in his long-term memory.