Tether (USDT) is a stablecoin available on several blockchains that aims to maintain the same value as the US dollar. The company behind Tether, Tether Limited, claims to hold reserves that fully back each USDT. As of 2021, USDT is the most widely-used stablecoin in the world, with a market cap over $30 billion.
At this time, i believe Coinbase only supports ERC-20 USDT running on the Ethereum blockchain. i think only ERC-20 usdt token supported by CoinBase, you can use ERC-20 Pionex address, which is starting with 0x. However, pionex itself supports multiple networks so you can use almost all networks to deposit USDT to your pionex account