I don't see Tether or USDT, only USDC as options on Coinbase. I've never heard of Tether, you picked that just to get it out of Bitcoin before Bitcoin drops?
USDC is an Ethereum based token used by coinbase, it's similar to USDT
https://www.coinbase.com/usdchttps://support.coinbase.com/customer/en/portal/articles/2958465-usd-coin-usdc-faqI do want to park the $ until bitcoin goes down. As another crypto currency maybe but don't they sort of track bitcoin in price? Whenever bitcoin is high litecoin is high too. I mine that a little so I watch it. I don't watch the rest.
then you can exchange your BTC to USDC and store it in your coinbase account
I don't know whether you can do it directly in your coinbase wallet or not
you probably have to do it on gdax exchange which is also owned by coinbase