Can you please assist of how to upgrade as below my iMac version 10.11.6 to catalina version 10.15 ?

Please see my imac version detail as below:

  Model Name: iMac

 Model Identifier: iMac8,1

 Processor Name: Intel Core 2 Duo

 Processor Speed: 2.8 GHz

 Number of Processors: 1

 Total Number of Cores: 2

 L2 Cache: 6 MB

 Memory: 2 GB

 Bus Speed: 1.07 GHz

 Boot ROM Version: IM81.00C1.B00

 SMC Version (system): 1.30f1