My ex came in the house, unplugged the garage door opener and jammed the doorknob of the door into the garage. How do i get the garage door open
Virtually all doors that are between the house and garage open into the house. This means that the hinges are visible from the house side. One alternative is to remove the hinge pins and the door should be able to be pulled inwards toward the house. Modern doors of this type will be a fire break type of door and may be fairly heavy so get assistance if needed to handle moving the thing.

Now you can then figure out the door knob issue from both sides now. If the knob has been broken to the state of non-usability you can replace it at fairly low cost. If necessary there are semi-destructive ways to cut off and removing a broken knob if it has been damaged beyond normal removal methods.  

Do yourself a huge favor and get the other entry door locks re-keyed or replaced as soon as possible to prevent access by unauthorized persons that may have copies of the original keys.