Q: How do I know what iPad I have. How can I tell what it's is if it is a iPad 2 ,3,4

Check iPad model with the Serial Number

https://selfsolve.apple.com/agreementWarrantyDynamic.do

You can also use this:

https://supportprofile.apple.com/

Identifying iPad models

http://support.apple.com/kb/HT5452?viewlocale=en_US&locale=en_UShttp://support.apple.com/kb/HT5452?viewlocale=en_US&locale=en_US

Identify Your iPad

http://www.ifixit.com/Info/ID-your-iPadhttp://www.ifixit.com/Info/ID-your-iPad

For information on your iPad (model, date of production, etc), enter your serial number at this site. Information, based on the serial number, will be shown.  http://www.chipmunk.nl/klantenservice/applemodel.htmlhttp://www.chipmunk.nl/klantenservice/applemodel.html

 Cheers, Tom