A large area of sand dunes in the desert is called a dune field. A large dune field is called an erg.
Such a large area could be classed as a desert. But, a desert doesn't have to be entirely of sand and dunes. Antarctica is also classed as a desert.
The Sahara Desert, N. Africa, is often given as an example of a huge area of shifting sand dunes. Though, actually, the dunes form only a small part. The main part consists of rocky 'hamada': high, largely barren, hard, rocky plateaus, with very little sand.
Dunes would be more prevalent in desert areas with an abundance of fine sand, few plants and a persistent wind.
The Kalahari desert is the large desert in southern Africa
In most deserts, sand dunes are only a small area covered by the desert.
Sand dunes are likely to be in a desert
The Carcross Desert is a small area of sand dunes in the Yukon. It is not a true desert, however.
Actually, Jericoacoara is not a true desert but and area of sand dunes and beach in Brazil.
There is no limit to the number of sand dunes in any particular desert.
Large sand dunes are one feature of the Sahara.
Yes, there are sand dunes in parts of the Sonoran Desert.
There are no true deserts in Nebraska. In the central part of the state there is a large area of stabilized sand dunes but the area receives about twice the annual rainfall of a desert.