Garmin support faq in website
Question: How many POIs can I fit into my GPS device?

Answer:
There is no set limit on how many POIs can be loaded into the Garmin device. This depends on the size of the POI files and the space available for POIs. The size of the loaded POIs will depend on the amount of text included with each POI and the size of any included bitmaps. Since POIs can be loaded into internal memory or onto SD cards, the space available will vary widely. Typically, the user should be able to fit more than 3000 POIs onto a unit. If the available space is exceeded, POI Loader will tell the user how much space is available in the device and how much space would be required to fit all the POIs that were chosen.