I went to advance auto parts to get brake shoes for my 96 Ranger, and they had two different sizes 9 x 1-3/4" and 10 x 2-1/2". How do i find out which one without having to tear it all down?

__________________
2003 Ford Ranger Fx4 Lvl II, 4.0L V6, 5-Speed, with Manual Transfer Case
99K mi., Explorer Disk Brakes (In Work), 3" body lift with GoodYear DuraTrac 33x12.5's on 15x8 DC-2 rims, Kenwood Excelon HU, with Kenwood 6x8 all around, 08+ Mirrors and Tails.