Memory sticks have lots of other names - USB drives, USB Flash Drive and so on. But they are all basically the same thing.
They come in different size memory, the larger the memory the more they cost.
They come in GigaByte memory size - known as "GB"
So you can get 8GB, 16GB, 32GB, 64GB and so on.
Now if you are not very technical then I will be rather blunt here, but copying all your personal files from your computer to a memory stick is not easy if you are not technical and have never done it before.
It is easy to accidentally delete your files rather than copy them if you don't know what you are doing.
Do you have a friend or relative or neighbour who could do it for you?
A person with some computer knowledge could probably do it in 10 minutes, but to try to explain how to do it will be quite complex.