Just some sourced dates.
Most bacteria can be seen with a light microscope (usually about 100x magnification). Viruses are considerably smaller, as they are merely nucleic acid surrounded by a protein shell as opposed to an entire living cell. Viruses typically range from 20-400 nm, meaning you need an electron microscope to see them.
https://www.quora.com/What-type-of-microscope-would-I-need-to-see-viruses-and-bacteria-live-in-their-natural-habitat?share=1
The first prototype electron microscope, capable of four-hundred-power magnification, was developed in 1931 by the physicist Ernst Ruska and the electrical engineer Max Knoll.[
https://en.wikipedia.org/wiki/Electron_microscope