There are many ways to get USD Tez (USDtz) — from credit cards, to exchanges, to minteries
In most cases (for 'small amounts') you'll get your USDtz from an exchange. This includes AMMs (Automated Market Makers) like Quipuswap, and Smartlink Vortex, as well as cross-chain bridges like TezEx (Tezos Exchange)
If you want to buy USDtz for USDC 1-1 without the slippage or liquidity limitations of exchanges, and perhaps you are seeking enough funds to provide liquidity to those exchanges, using the services of a trusted mintery may be a better path
If you don't want to go through a Mintery, and would rather mint on your own, then you may qualify to enroll as an individual minter as a Mintery. (You may also qualify to create a Mintery yourself, especially if you are a Tezos baking service in good standing)
You can also use a credit or debit card to buy or sell USDtz with Wert.io