what is the file format? I need a FAT32 how do i know what file format these are?

A file format is a systematic method, or convention, used to write data to a disk. An analogy would be a human writing down information on a piece of paper; one format would be English text whereas another format would be Russian language in Cyrillic text. Not everyone would be able to understand or decipher the information if, for example, you could not read Cyrillic text or understand Russian then you'd have the human equivalent of an "unsupported/unreadable disk error".

The good thing about FAT32 is that it is not proprietary or exclusive to Apple or Microsoft and can be read and written to by virtually any computer or device. The downside with FAT32 is the file size limitation of about 4GB, which only matters if you are dealing with big files. If you wanted to store files larger than 4GB you would probably want to use exFAT, otherwise FAT32 should work fine for you.

You can format disks by connecting it to a computer and using the disk utility program to create volumes, partitions and decide what format to use.