I transferred about 0.54 BTC and I cannot find this on Blockchain.com. Can anyone help?
Firstly, I would use Blockstream.info or mempool.space, not blockchain.com for your online block explorer. 

Second, depending on the exchange, they could batch withdrawals at a certain time each day, or they could set a very low fee, which means it would take a long time to be confirmed. 

As was said in the comments, you could've been scammed. I have never heard of Dasset before. 

Lastly, for each transaction, generate a new receive address to ensure privacy.