No need to get beligerant just because you don't like someone's answer. What you've been told so far is actually spot on, but to elaborate...
Like rolli59 said, your AiO PC is basically a big laptop, all the internals are actually laptop bits, not desktop hardware. The M in Geforce 210M indicates that you have a mobile chipset version of the Geforce 210M. Mobile GPU's are almost always, and I mean 99% of the time, soldered to the motherboard which makes replacement difficult for two reasons. 1) It's soldered, and 2) many mobility chipsets sit on custom sized printed circuit boards (PCB's) which fit into a specific place on the motherboard while fitting the notebook chassis. While standards for mobile chips do exist their use by mainstream manufacturer's is rare which means even if you were able to find a better chip it would have to be the right fit as well. Upgrading your GPU also means additional power will be needed and additional heat will need to be dissipated, two things which your AiO PC probably can't do/handle. Finally, mobile versions of GPU's are not readily available on the consumer market. You can find used ones on ebay and amazon, but even then it's buyer beware.
+1^ Great answer!