The rights to the animation. How to use it?

please define "my asset"?

if this Unity project is a game, image, vid etc then yes you can sell it ... the fact that you happened to use Mixamo animations to make it doesn't matter and no you don't need to credit Mixamo but most people can spot Mixamo animations anyway

if this project is the animation or model files then no you can't sell them because the animations belong to Adobe so lets say you make a custom model and use a Mixamo animation to show how the model looks walking around... you are allowed to do this and sell the model you made but you could not include the Mixamo animation in the file they download after paying for it because that isn't yours to sell, however you could give them a link to the Mixamo webpage and let them just download the animation themselves & you already showed that it works on your model

hi! i think you might be able to, but you would probably have to credit them. you should probably wait until someone who knows for sure answers, but i THINK you should be able to as long as you credit them.