If your garden looks a bit like the image below, then this is the FAQ for you!
There are two ways to select one of the Baskets or Hampers so that you can see the item information as in the image. You can tap and then dismiss the pop-up with the Gem purchase price by tapping on the 'X' at the top right, or you can press and hold on the Basket/Hamper and this will allow you to bypass the pop-up.
Tapping on the 'sell' button will give you the coins stated in the information bar. You may have to tap again or tap the confirmation button in the separate pop-up for the more valuable hampers.
If your coin storage is full, then you will be given the option to delete.
If you cannot see that information bar, then please tap on the small arrow that shows at the bottom of the Home Garden screen; this should be present in your game always and is located centrally.