In a 6-quart slow cooker, combine the 2 (10.5-ounce) cans condensed cream of chicken soup, 1 (14-ounce) can chicken broth, 1 cup chopped onion, 1/3 cup finely chopped celery, 1/2 teaspoon poultry seasoning, 1/2 teaspoon garlic powder, and 1/2 teaspoon black pepper. Stir until evenly combined.
Add the 3 boneless, skinless chicken breasts to the slow cooker, turning to coat them in the sauce. Cover and cook on LOW for 4 hours, until the chicken is cooked through and tender.
Remove the chicken from the slow cooker to a plate or cutting board. Use two forks to shred the chicken into bite-size pieces, then return the shredded chicken to the slow cooker and stir to combine with the sauce.
Working with the 8 refrigerated biscuits, flatten each biscuit and cut each one into 8 pieces.
Scatter the biscuit pieces evenly over the top of the chicken mixture in the slow cooker, gently pressing so they contact the sauce.
Cover and cook on HIGH for 60 minutes, until the biscuit pieces are cooked through and puffed.
After 60 minutes, stir gently to combine the dumplings and chicken, then cover and continue to cook on HIGH for 10 minutes. Serve.