I read that you have millions of b cells. how does one b cell find the right specific antigen it fits to if there's so many of them?

Antigens get held...: Each B cell recognizes only 1 unique antigen. We need > 1 million B cells to ensure most antigens are recognized. Collectively, B cells could likely recognize any organic molecule that could exist. The process does not rely on random encounters. Specialized cells trap and hold antigens where circulating B cells get the chance to recognize them.