There is also a very good possibility you can install Windows 10. I have installed Windows 10 on both a 2007 and a 2011 iMac computers even though Apple does not officially support Windows 10 on either computer.
The easiest method of installing would be to use the optical (DVD) drive. If you have the latest ISO release of Windows 10, then you will need a dual layer DVD (DL) to burn the image to.
If you do not have a working DVD drive, the you can use this complex method to install.
I should also warn that one of the Boot Camp Support Software files may need to be replaced if you install the latest Window 10. See this question for more information.