Floor duct

WARNING: This page is about a different car, the 2003 Nissan Altima. However, it is still accessible from the selected car via links, so may be relevant.

Remove the carpet. Refer to "FLOOR TRIM ".
Release foam tape and slide floor duct rearward to release from clips.

Fig 1: Releasing Foam Tape And Slide Floor Duct Rearward
Courtesy of NISSAN MOTOR CO., U.S.A.