Slave sales could be private, or public auctions. If you mean, where are there records of slaves that were sold, you might look in the deed books of the localities. Transfer of ownership of slaves was recorded by deed. The deed books would list them in the indexes under grantor and/or grantee names (of the purchaser or seller). Sometimes there will be a notation that it is the sale of slaves, rather than land. Also, if there are any slave dealer records for the locality you are researching, that might be an option as well. Hope this helps, Elizabeth