Partitions: Create Bootable USB to load Windows 10 install
Your question lack sufficient information to properly answer. I will assume the machine where you wish to install Windows is a PC and not a Mac.

Certain Windows 10 ISO files can contain at least one file to large to be saved on a FAT32 formatted volume. However, when the same release of Windows 10 is saved to a USB flash drive by the Windows media creation tool, smaller files are substituted for the ones to large to fit on a FAT32 formatted volume.

One solution you be to install VirtualBox on you Mac. This is a free product. You can then use your Windows 10 ISO file to install Windows as a virtual machine. Once booted to Windows, you can download the free media create tool from Microsoft. This tool can be used to create a bootable Windows 10 installation USB flash drive. 


  Note: After installing VirtualBox, you will need to install the VirtualBox Extension Pack in order to access a physical flash drive from the virtual machine.