UPDATE - NOT A DUPLICATE:
The reason why I do not think this is a duplicate is because I need to access data within a program called Wekan. I do not know how to extract that data from Wekan by mounting the ISO, which is why I am hoping to boot from the ISO.
I created a full backup of Ubuntu 16.04 using the command:
sudo dd if=/dev/sda of=/some_folder/backup.iso
So the backup includes the full drive, including all partitions etc.
I then installed Ubuntu 18.04 and realized I forgot to copy over something from Ubuntu 16.04.
Is it possible to boot into the 16.04 iso file and load the operating system using 18.04?
Also, the 16.04 drive is encryption and I do have the passphrase to access it.