How deep?
Under pavers, the Interlocking Concrete Pavement Institute and Belgard both give a 1-inch layer of bedding sand on the compacted base. For fill, a sandbox or leveling, measure the depth you need.
Bags or bulk
Quikrete sells its paver sand, play sand and all-purpose sand in 0.5 cubic foot bags, and Sakrete’s play sand yields 0.5 cubic feet a bag, so one cubic yard is 54 bags. Two suppliers publish 2,600 lb per cubic yard for masonry sand and 2,700 to 3,000 lb for bedding sand, depending on moisture.
Joint sand is a separate product
Polymeric sand for the joints between pavers is sold by coverage, not by volume. Use the polymeric sand calculator for it, and the paver base calculator for the base and bedding layers together.