Issue with animation

Video of my issue: link to the video
I am using Mixamo animations and models.
I’m having trouble with positioning the arm of my character to look like the other character standing up. He’s supposed to be looking at his phone, but the one sitting has his arm closer to his chest. I want it so that it looks like the one standing up, looking at his phone normally.

How do I achieve this?

Either Edit the Animation in Unity or other 3D Engine or use IK Chains and edit the Arm position