They will all almost certainly fire/flash - so from that point of view they will work. As the others have said, any function that require communication between the flash & camera - eg automatically recognising the aperture set on the lens... will not work. However that isn't necessarily a problem - in fact working with manual equipment will teach you more about your hobby that fancy auto stuff.
useful features to look for are: -
1) a bounce head (& swivel) - this enables you to bounce light off ceilings (& wall) to give a softer more diffuse light which creates more flattering shots
2) 'auto' mode(s) - this is a setting in which you tell the flash, usually by means of a slider, what aperture (from a set selection eg f4 or f8 for a particular ISO) you have set on the camera. The flash then has a sensor which measures the amount of light coming back from the subject and adjusts the light output to give the correct exposure
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