How can I get my Photo Contest email entries into Convertkit?

Hi there - ran a contest earlier this year before starting to use Convertkit and now wondering how I can extract those emails and see if I can get them signed up to my email list.
Is there any way to extract these and then I can get them into convertkit to see if I can get them onboard (I’m running a comp so can see if I can warm them that way) giving I prob should have thought about ensuring they knew I’d be adding into email list at time of comp!!!

The benefit of hindsight!