If i wanted to look at a onion cell what type of microscope would be best to use

It is best to use regular light microscopes to observe that.

For simple structures, onion cells doesn't require a very large magnification. Magnifications for such as 100X or 150X is already enough to determine the different structures of onion cells such as cell walls or cytoplasm.

It is not very suitable to use a electron microscope especially as high school or college students, as electronic microscopes can be really expensive, usually only top universities have them. Also, it is quite complicated to control the microscope comparing to the common light microscope that we can easily find in many school laboratories. They're easy to function and they're a lot cheaper.

So, it's best advised to use a light microscope, unless if you're really into studying very detailed structures and you're experienced in doing these sorts of things, then you should use a electron microscope.