The product you mentioned, the "Blazing Needles Solid Microsuede Double Corded 8" to 9" Futon Cover," is a futon cover, which means it is designed to fit over a futon mattress. A futon mattress is capable of being converted into a bed when placed on a futon frame that allows for this function.
To clarify, the cover itself does not transform into a bed; rather, it is used to cover a futon mattress that can be converted into a bed. If you have a futon frame and mattress that can be adjusted, then yes, it would turn into a bed when set up appropriately. Always make sure that your futon frame and mattress are compatible with each other for the best results.