Where are the spark plug 1, 3 and 5?

For a 1998 Avalon with the 6-cylinder,3000 series engine, you have 3 coils. Each coil does 2 cylinder spark ignition. So, follow the wires from the coils, you can saw on front side facing you after opening hood. The 1,3, and 5 are located behind engine, between engine and firewall. A little bit harder to access but you can with universal joint on racket extension. Since you can go about 100K on plugs, I go with at least the two prong type, near the expensive end of plug cost. $ 36 to $ 40 plug set is worth the time and fustration of changing out $ 16 plug set.