Hi Lyla,
Insert the SD Card into your PC
In Windows File Explorer, note down the drive letter of that SD Card
Click your Start Button, type cmd and hit Enter
Run the following command (replace X with the drive letter of your SD Card), then hit Enter:
(you can copy and then right click in the command window to paste automatically)
format /FS:FAT32 X:
That should format your SD card to Fat32