How do I take the child lock off on the back doors?

Hello,

Are you able to unlock the door?
Is the issue only one of the rear doors?

Keep in mind that the child lock prevents the door from opening from the inside. It does not affect the door operation from the outside.
If the door is unlocked but it is not opening, then the issue could be a faulty door lock actuator. It might not be releasing the door.
To access the door lock actuator the inner door panel will need to be removed first. Which could be difficult with the door being closed.
After removing the panel, you will be able to get to the actuator.

https://www.2carpros.com/articles/test-or-change-electric-power-door-locks

Let me know if you have any questions.
Thank you.