1. The Hobbit. You don’t have to read this first as it’s not part of the Lord of the Rings series, but it makes more sense if you do.
2. The Fellowship of the Ring.
3. The Two Towers.
4. The Return of the King.
Numbers 2-4 are the actual LoTR books, but The Hobbit is the prequel. You could also read the Silmarillion afterwards or beforehand, but it’s not technically part of the series. (Note: If you read the Silmarillion, it kind of classifies you as a LoTR nerd). Hope this helps!