
Normally, when you delete pictures (or any files) from a memory card the data itself isn't deleted, just the information that says where the rest of the data for those files is located. The area where the deleted picture data was stored is also now marked as free space so it is available to the system for any new files to be written there instead.
One of the easiest ways to see if your deleted pictures can be recovered is to download some photo recovery software.
You'll then need to connect your phone to the PC using the USB cable that probably came with it, or if not, take the memory card from the phone and put it in a card reader connected to the PC.

