If the MicroSD card is brand new then there is no formatting required. Simply put it in your device and it will be usable from the word go. If the device needs to do anything it will most likely prompt you or format itself automatically or when you first save an item to it.

Are micro SD cards already formatted?

Note that most Micro SD cards that are 32 GB or less come formatted as FAT32. Cards above 64 GB are formatted to exFAT file system. If you are formatting your SD for your Android phone or Nintendo DS or 3DS, you will have to format to FAT32.

Do SanDisk Micro SD cards come formatted?

When you buy a SanDisk micro SD card, it will be formatted properly. However, there are times when you want to erase everything on the card or possibly eliminate errors you might see when using the card.