Does anybody know how to evaluate the impact of physical exercises on memory for elderly people?

You’re welcome.

Thanks for your advice!

It looks like you will need to use a few different measures:
1) Sink, K. M., Espeland, M. A., Castro, C. M., Church, T., Cohen, R., Dodson, J. A., ... & Williamson, J. D. (2015). Effect of a 24-month physical activity intervention vs health education on cognitive outcomes in sedentary older adults: the LIFE randomized trial. Jama, 314(8), 781-790.
Where they used, "...primary cognitive outcomes were measures of psychomotor speed, attention, and memory (Digit Symbol Coding task and Hopkins Verbal learning tasks). Additional neuropsychological tests and rates of incident MCI and dementia were also evaluated."
2) Lautenschlager, N. T., Cox, K. L., Flicker, L., Foster, J. K., Van Bockxmeer, F. M., Xiao, J., ... & Almeida, O. P. (2008). Effect of physical activity on cognitive function in older adults at risk for Alzheimer disease: a randomized trial. Jama, 300(9), 1027-1037.
Where the ADAS-Cog (Alzheimer’s Disease Assessment Scale-Cognition) was used.