Not a basic question at all, the discrepancy between what random trackers show and what you actually get at point of sale is a real thing and it catches people out. What I've been using is https://paybis.com/sol-to-usd/ — it pulls live rates and gives you an actual conversion rather than just a market price that doesn't account for anything practical. Handy to have open before you make any decisions about moving SOL around, especially when the market is doing something interesting and you want a quick read without committing to anything. Bookmarked it ages ago and still use it regularly.