how can i know the generation of my ipad

See: Identify your iPad model - Apple Support

You first identify your model (Settings > About) and then use Google or other search tool to find out. Wikipedia has an excellent cross reference for iPad models:

https://en.wikipedia.org/wiki/IPad

The signature in your question suggests you have a very old iPad 2 (i.e. the second generation of iPad) - this being limited to iOS 9.3.5/6.