The native Sui bridge is primarily for SUI tokens, facilitating transfers between Sui and Ethereum. For USDC, you'd typically use the Wormhole bridge. USDC on Sui is usually a Wormhole-wrapped asset, so Wormhole is the standard path to bridge it back to Ethereum mainnet.

The website for SUI native bridge is https://bridge.sui.io/. However, USDC is not currently supported by the native bridge, only USDT is. If you specifically want to use native bridge then you can swap your USDT to USDC, transfer and then swap back on Ethereum mainnent. But you would have to pay extra fee for those swaps. Alternatively, you can use a third-party bridge like this one: https://portalbridge.com/