SSIS while upgrading SQL server
Unfortunately you need to migrate your 2005 packages to 2012 using Data Tools. Depending on the complexity of each one this task will be more or less complicated. Here some useful links that I have used in the past:

https://devinknightsql.com/2012/05/16/upgrading-packages-to-ssis-2012/

https://sqldusty.com/2012/03/19/upgrade-2008-ssis-packages-to-2012-like-a-boss/

https://blogs.msdn.microsoft.com/mattm/2008/03/22/package-upgrade-wizard/