Click on your platform to show the formatting instructions for your SD card.
Here is a link that shows you how to reformat an SD card (or MicroSD card) on your Mac. The steps are also written out below.
Connect the SD card to your computer by using an external card reader. Save all the files from your SD card that you want to keep to your computer before moving to step 2. Formatting the SD card deletes all the data off of the card.
Note – If you’re using a Micro SD card, please insert the Micro SD card into the SD card adapter that came with card. Connect the SD card adapter to your computer by using an external card reader.
Also note – Mac OS 10.6.5 or earlier does not support exFAT format, which most 64 GB SD cards are formatted to. This means that you won't be able to format or use exFAT card on your computer. In this case, we'd recommend either upgrading your OS to 10.6.6 or later, or using an SD card that's already formatted to MS-DOS (FAT) or FAT32 to complete the below steps.
Open Disk Utility. To do this, click on the magnifying glass in the top-right corner of your computer screen. Type “disk utility” in the search box that opens, then click on the “Disk Utility” Application that comes up.
Find the SD card in the left side of the window. It’ll be named something like NO NAME or UNTITLED.
Click the ERASE tab in the middle of the window.
Next, click on the Format dropdown menu. Select MS-DOS (FAT) if the card is 32 GB or smaller. If it’s a 64GB card, please select ExFAT.
A message will appear asking, “Are you sure you want to erase the partition “[YOUR SD CARD NAME]?” Click Erase. The computer will delete the contents of your SD card and format it. You’re all done.