Upgrading

I have an old app that is currently using CodeIgniter 1.7.0.  I am trying to upgrade it to use CodeIgniter 2.1.0.  Can I go directly to 2.1.0 or do I have to step thru each upload until I get to 2.1.0??
I've tried to go directly to 2.1.0, but now I'm getting the following trying to get to the initial login page.

404 PAGE NOT FOUND

The page you requested was not found.

You need to do it step by step, sometimes the changes are made to the application folder also.

What did you Try? What did you Get? What did you Expect?

Joined CodeIgniter Community 2009.  ( Skype: insitfx )

How do you do it step by step, when we are at CI1.7.0 and on the CodeIgniter download page, they only start at CI2.0????  I don't have the download for anything before CI2.0.....

See https://codeigniter.com/userguide2/insta...ading.html

ci-phpunit-test | CodeIgniter Testing Guide | CodeIgniter 3 to 4 Upgrade Helper

See https://codeigniter.com/userguide2/insta...ading.html

Thank you!!  Where are the downloads for 1.7.1-2.0??

I found this:
https://web.archive.org/web/201308160459...loads.html

ci-phpunit-test | CodeIgniter Testing Guide | CodeIgniter 3 to 4 Upgrade Helper