I assume that this is the standard belt that you need
GOODYEAR Part # 4050345 5 Ribs / Effective Length 34.5" / Outside Length 35.25"
Poly-V; Alternator and Power Steering
or
ACDELCO Part # 5K345 {#88932577} K05 21/32" x 35 1/4"
BELT,SERPENTINE ALT & P/S
Go to
Goodyear Gatorback Poly-V Serpentine Belts - SummitRacing.com and select the length belt you need then take the part number into the store and ask for that part number.
I do not think you will have a problem finding the length that you need since they have sizes from 20" to 88"