I will suggest please learn before you make a transaction. Because if you aren't familiar with the crypto-currency transaction then there is a risk of losing funds. So please study as much as possible. You may ask YouTube or Google what you need to learn. But keep in mind, just follow them for learning purposes. Don't believe them blindly, because we don't know who is a fraud and who is good. For more help, you may read an article about USDT in coinbase:
https://help.coinbase.com/en/coinbase/getting-started/crypto-education/USDTMake sure you are making the transaction in Ethereum (ERC20) network. Because coinbase does not support any other network for USDT transactions. This means if you send a transaction in another chain instead of ERC20 to coinbase then you will lose funds forever. Although a few exchanges detect address automatically, but not all and we don't know from where are you going to send funds.