Yes, some do require that you write an essay on your experience at a pharmacy. I know Texas Tech for sure requires that. But you can shadow a pharmacist or simply just interview them. I worked at a pharmacy for about a year. I know UT does not require that or Loma Linda or Texas A and M. It seems most schools do not require this specific experience.
If I were you, I would get a job in a retail pharmacy or volunteer in a hospital pharmacy. You should probably work in a pharmacy for at least 3 months. I believe some schools put more weight on pharmacy work experience than GPA and/or PCAT. Good luck.
Most schools dont have a set number, but I would shoot around 100 hours if you can. It shows that you are interested in it for more than just a recommendation letter and have seen enough of the goings on to know what the Pharmacist handles on a day to day basis.