I broke the front glass screen

I would like to replace the broken glass but do not know how to identify the correct glass the the machine I have. Here is the info from the system profiler;

Model Name: iMac

Model Identifier: iMac11,2

Processor Name: Intel Core i3

Processor Speed: 3.2 GHz

Number Of Processors: 1

Total Number Of Cores: 2

L2 Cache (per core): 256 KB

L3 Cache: 4 MB

Memory: 12 GB

Processor Interconnect Speed: 5.86 GT/s

Boot ROM Version: IM112.0057.B00

SMC Version (system): 1.64f5

Serial Number (system): W80431ATDB7

Hardware UUID: 2155B769-9899-5715-84F1-124340A9525B

but how do I make sure to order the correct glass front for this machine and where can I find it?

thank you