web with map arcgisonline-define query

[lauralol]

Hello,

I am creating a website with a template and a map in arcgisonline.com. I have 1 map with two layers: points and poligons. I would like with this layers to make query, find and buffer, but I dont know what I have to write in:

var queryTask = new esri.tasks.QueryTask("http://sampleserver1.arcgisonline.com/ArcGIS/rest/services/Demographics/ESRI_Census_USA/MapServer/1");

How do i say to the program the layers contained in arcgisonline?
Thank you

Regards