You hold XMR and the dollars have to land on Ethereum specifically — a DeFi position, a service that accepts only ERC-20 deposits, or a long-term stablecoin balance in the wallet where the rest of your Ethereum assets live. If the receiver would take TRON instead, the TRC-20 route is cheaper to move on afterwards; this one is for when Ethereum is required.
Monero and Ethereum do not interoperate. The XMR is received on the Monero chain — 5 confirmations, about 11–24 minutes — and USDT is then transferred to your 0x… address by an Ethereum transaction. You never hold anything in between.