All of a sudden I lost power?

Hello,

It sounds like you might have a faulty alternator.
As you mentioned the car will stall as soon as you unhook the jumper cable that is a indication that the alternator is not putting out enough to the battery to keep the car running.
When you have bad alternator, it will drain the battery and sometimes it can affectively make the battery go bad.
In order the replace the alternator you will have to remove the serpentine belt.

Here is some helpful information:

https://www.2carpros.com/articles/how-to-check-a-car-alternator
https://www.2carpros.com/articles/how-to-replace-an-alternator

I have attached diagrams for your reference.

Please let me know of any questions.
Thank you.