You will need to export your comics out of Comic Life, rename the files and then import them back into Comic Life 3 using iTunes File Sharing.
Please see below for detailed instructions:
1. Open up the "old" Comic Life on your iDevice
2. Swipe Left, to bring up "Collections"
3. Click on the collection that has all your comics in them (by default it is "My Comics")
4. Under "Export Collection To:" choose "iTunes"
5. Then for "Copy collection to iTunes as:" choose "Comic Life Archive"
6. Now open up iTunes on your Mac or PC
7. If you are not familiar with iTunes File Sharing, please check out: http://support.apple.com/kb/ht4094
8. Navigate to "Comic Life" in the File Sharing section, on your iPad using iTunes
9. You should see the comics you have created, select all the comics you want (hold down command key on keyboard, and click on each file)
10. Drag them out into an empty folder in Finder
11. Replace the file extension for each file from ".cl2arc" to ".comiclife".
12. Now navigate to "Comic Life 3" in the File Sharing section, on your iPad using iTunes
13. And drag in all the files you just renamed into the same place they were in "Comic Life" (but now in "Comic Life 3" as chosen in step 12)
14. Once all files are copied over, pick up your iDevice and open "Comic Life 3".
15. Tap the Tools icon (the spanner in top right corner)
16. Choose "Collections" > then Import > then Copy from iTunes
17. Tap on each file you wish to transfer (a tick will be placed to show confirmation)
18. Tap "Import" down the bottom
19. Your selected comics will then be imported into Comic Life 3.
20. You have made it to the end - congratulations!