I bought a bike for $20; thinking about doing a simple conversion to the existing wheels, with a single speed kit. Just something to ride to and from the store. Don't want to put a lot of $ into it.
However, I am wondering what size wheels would fit; it's got 26x2.125 on it now. Will a 700x28c fit? It looks like a mountain bike frame.

Is this correct?
700 C = 622mm
26" = 559mm