2032 in the manual but you need to understand: desktop computers do not need a CMOS battery to work. The battery just allows system date and time to be remembered when power is off. If the machine does not work without a battery, it will not work simply if you put a battery in. In other words, you have some troubleshooting to do. You have posted this question in lots of forums across the web, and have been told this already.
2016 is 1.6 mm thick, 2032 is 3.2 mm thick, but same 20mm width; same voltage. If battery holder clip will allow either, 2032 will last longer.