Hi Blhaas1, congratulations on your new A10-70 and welcome to the forum. Nice of you to become a member of Android Tablets.
A Micro SD Card (MSD) is what you're after. They're intended as space to store your media files.(eBooks, pictures, videos, movies, music files etc.)
Those cards are available in many memory sizes, and Lenovo says your tablet will accept up to 32GB cards without a problem. How much media do you plan to have? That's the size to get.
They're typically available as Class 2, 4, 6, & 10 where the Class indicates the transfer speed of the MSD in MB/s. If you plan to watch movies and videos stored on your MSD, you should use a MSD that's Class 4 or higher to get smooth playback. (I buy the least expensive Class 4 cards available, but from a reliable store, and have never had a problem.)