Cars 2 was the first Pixar Cars film released with a 3D theatrical presentation.
The 2011 sequel was presented in Disney Digital 3-D as well as traditional two-dimensional formats. Its international races, aerial chases, and spy-thriller action gave the filmmakers many opportunities to use depth and large-scale movement in the theatrical experience.
The original Cars was released in 2006, before the franchise adopted 3D presentation for a feature release. Cars 3 followed in 2017 and was also released in 3D in selected markets, but it was not the first Cars film to receive that treatment.
This fact concerns the theatrical presentation format, not the animation method. All three main Cars films are computer-animated Pixar productions; 3D presentation refers to how audiences could view the film in theaters.