Yes - they need to be trained to eat hay. Hay is not as tasty as pellets and, coming from a pet store, they likely never had hay (it’s messy). Assuming they’re 4-6 months old you can give them alfalfa for a few weeks before transitioning to Timothy. You can also mix it for a month or so. After that move to all Timothy. Alfalfa is like cupcakes for an adult rabbit.
Their pellets depends on their weight. My 4lb adults get 1/4 cup of pellets per day. Many feed 1/8 cup pellets per 5lbs of rabbit. Check their weight and bone feel to be sure it’s the right amount for them.
Only do fresh greens a few bites a day and check for soft poops.
Be sure they’re eating their “blackberry poops” (cecotropes) at night. If you see them piling up, then their diet is too rich or too much.