Where can i find mac os x 10.5? i cant find a link.?

i am one of the most technology illiterate people out there. i bought an ipad 2. I turn it on and it shows an image of an itunes icon and I ume it means I need to connect it to itunes. I connect the ipad 2 to my and it says i need to download itunes 10.1 or higher. I go to download itunes 10.2 and it says "Couldn't open "Install iTunes.pkg". This package type requires Mac OS X 10.5." I download Mac os x 10.6 and it says "Couldn't open "Mac OSX Upd 10.6.7 for MacBook Pro Early 2011.pkg". This package type requires Mac OS X 10.5." i cant' find a mac 0s x 10.5 download link. can you help me with this? thanks