I see. My bad, I was reading it on my phone. If you don't have the flashdrive connected, and you only have an nvme drive in your laptop, then the sdb and sdc devices would be from your card reader. I am thinking sdc is the card reader since it shows 30.6M size. However that would be a very small card in 2026. It's a little surprising to me it's not even showing partitions for sdb or sdc in lsblk output.

Is the card pre-formatted (or did you format it)? Is it readable on another device?

Edit: I forgot to mention: if your card is formatted as exfat, you may need to load the exfat module:

sudo modprobe exfat
sudo lsmod | grep exfat

If you have it, you should see exfat in the output from the second command. More information here