The majority of the Bellas introduced in the first film, including Kendrick's Beca, have graduated from Barden and are trying to make it out in the world.

Source: https://screenrant.com/every-pitch-perfect-movie-ranked/

When a fellow student hears her singing in the shower and urges her to audition for the school's all-female a cappella group, the Barden Bellas, Beca gives it a shot and soon finds herself a member of the choir.

Source: https://www.popsugar.com/entertainment/choir-movies-49137073