NFT sales are all logged and confirmed on the blockchain; your cryptocurrency wallet will have a transaction that will confirm each sale.
So you sold your NFT well done, now you want to see the transaction well. The beauty of the blockchain is that all NFT sales transfers and airdrops are logged and can be viewed by your web browser.
If your NFT was based on ethereum you most likely used the Metamask wallet to list the NFT for sale on a Marketplace such as Opensea, Simply login to your wallet and click on ‘View on etherscan’ from the menu.
Etherscan is the view for the ethereum blockchain that shows all transactions that have happened or are pending. The interface can seem a little too much at first with all the numbers and long addresses but with a little time browsing you can see the information you want and somewhat ignore the rest.
If your NFT was based on Solana there is Solscan does exactly the same and etherscan but for the Solana blockchain. Essentially all blockchains have their own version of etherscan they help users track and trace transactions by representing the blockchain in an easy to use frontend viewer.