[HELP] USDT asset in Coinbase wallet cannot be sent or swapped

Hello! I am relatively new and considerably inexperienced when it comes to all things crypto. After looking through reddit and other online forum, I figured it was time to ask here. I hope you can help.

I currently have USDT (Tether) in my Coinbase wallet. I am trying swap the asset for BTC and ETH. My issue is that when I select my USDT the app states, "This asset is on the BNB (Binance Smart) Chain network." Clicking past that prompt, my next prompt states "You need BNB before you can make a transaction on the BNB (Binance Smart) Chain network. It also states "To pay the network fee, you need to add BNB to your wallet. Alternatively, you can switch to a different network. The network fee goes tot network participants who process transactions, not Coinbase." When I try to send my USDT it states I need BNB, but Coinbase does not allow me to purchase BNB.

So, with all that said I have a few questions and any input is appreciated.

1. How do I go about swapping my USDT to BTC and ETH within the Coinbase app? The ultimate goal is to withdraw all my assets.
2. Do I need the Binance app to purchase BNB? I'm having troubles with this application allowing me to purchase any BNB, but if this is the way then I will figure it out.
3. What network should I purchase BNB on?
   

I've been at this for a few weeks in my free time and I'm starting to think that this Tether is unobtainable from my wallet. Any insight is appreciated. Thank you!