You can try the above or you can copy them to your computer then copy them from there to your SD card.
To do so.
1.Plug your tablet into your computer, if auto-play pops up click on import pictures and videos (if imported go to step 3) , go to your tablets' folders there should be a folder that says pictures. Your pictures and videos should be in there you also may want to check your downloads folder as well just in case you saved pictures from a text message or a website.
2.Copy all of the pictures and videos you want to save somewhere easily accessible on your computer.
3. After all of the pictures and videos are copied over then plug in your SD card and copy them to it, if your SD card is all ready inside your tablet then navigate to your SD card copy them from Pictures, on your computer, to wherever you would like on your SD card.