Just to fill in some blanks: By "memory card" I take it you mean the type of cards that are inside your computer (that is RAM, or Random Access Memory), you should know that this is called volatile memory. VRAM, though the V is almost always left off. You computer applies voltages that set specific bits to 1 or 0 in the RAM, and supplies a separate constant voltage that allows the RAM to maintain those settings. As long as that constant power source is supplied, your bits remain in RAM. Turn the computer off, the power goes away, and the information in RAM goes away. So a memory card can't be used to store stuff once it's been removed, unless you write your shopping list on it with a Sharpie pen.
Thumb drives and things like SD cards and solid state drives are made of what is called "non-volatile RAM". NVRAM. In these, a voltage is applied to set a bit, and through technical wizardry of some sort, that bit is maintained in memory, even after you remove the thumb drive from the USB port, or the SD card from the SD card reader, or the SSD from the computer.
As Jumanji points out, NVRAM isn't completely non-volatile. After several years, there can be significant loss of data integrity. So, for convenience and frequent use, an SD card or thumb drive is great. For zippy system performance, an SSD is great. But for critical files (and emotionally important files, like pics of family and friends and such), you are still better off putting things on a hard (spinning platter) drive, or a CD or DVD. There is even tape backup. The article below suggests as many formats as your machine can handle. Copying the files to your XP hard drive is smart.
The TV character Sheldon Cooper (The Big Bang Theory) has a "Mortal Enemies List" that he supposedly started in 1982, and that has been stored on a 5 1/4" floppy disk since then. In one episode, he felt the need to update that list, and found that the floppy had been corrupted. The point is, whatever you save your picture files on today will become obsolete. Make sure you make verified copies to new technology as it arises.
Backing up digital photos | Ask Jack | Technology | The Guardian
CD, DVD or SD: what's best for backups? | Ask Jack | Technology | The Guardian