how to format usb to FAT32

Disk Utility was mentioned. Make sure that View > Select All Devices is set up. Then you can win an entire USB drive if you wish. Select the thumb drive contents. when it shows up in the menu on the left. Then click on the "Erase" button and MS-DOS (FAT) will be a pull down option. It doesn't specifically say it's FAT32, but is is.

Applications/Utilities/Disk Utility.app

Format a disk for Windows computers in Disk Utility on Mac ...