Answer : An album
A collective noun is a ‘kind of noun’ that refers to a collection of things, people, animals, objects, and other stuff.
When you use a collective noun, you are implying that there is a collection or a grouping of items.
A few examples of this would be a hive of bees, a flight of stairs, a school of fish, a herd of cows, and an army of ants.
In this scenario, the best choice would be to get a stamp album. A cornucopia of stamps, or a significant collection, can be found in a philatelist’s album.