It has been over 12 hours and my migration is still Not finished

You need to tell us how you did the migration. The fastest, most reliable and most simple method is in Setup Assistant and Migration Assistant. If you tried it ANY other method, then stop the process, restart and use the Migration Assistant instruction in the link. If you do not have a backup of the old Mac, then MAKE ONE, you can still use the External Hard Disk to backup the new Mac.

The process can be time consuming depending on the Macs being used and the amount of data that is being transferred. 24 hours is not unheard of, but maybe leaning toward excessive.

What year models are the iMacs are you using?

How much data are you transferring?