SD card=memory card.
Memory card capacity is shown in the owner's manual. Do you have it? If not, download it from Canon. How much fits on a card depends on image quality settings and if shooting JPEGs or RAW or both. Total movie recording time on a card depends on movie recording size setting. Either one depends on available space on the card. You can have stills and video on the same card.
Stick to the full size, SDHC SD cards, which have a capacity of 32 GB or less. I realize the camera specifications says the SDXC SD cards, which have a capacity of 64 GB or higher, are also compatible. They are not compatible.
Based on personal experience [and] those of other forum members experiencing SD card issues with xxxxD camera bodies, the camera will give you frequent errors or just stop working with SDXC memory cards. When you switch to a smaller card, SDHC, then all the problems go away.
09/26/2023: New firmware updates are available.
08/18/2023: Canon EOS R5 C training series is released.
07/31/2023: New firmware updates are available.
05/31/2023: New firmware updates are available.
05/18/2023: New firmware updates are available.
03/30/2023: New firmware updates are available.