You need to write a few sentences about a good memory you had. It is impossible to help you with this since the answer is based on YOUR personal memories! I’d suggest picking something easy like a birthday or something and just write some sentences such as, “My 12th birthday party was one of my best memories” and “My favorite part about my 12th birthday was the presents I got. I got a ______, and a _______!”. Just things like that.
Hope this helps a little bit.