The "M" is not of much interest in pinball applications.

What you should do is match as close as possible the 'capacitance' of each one - EG 15,000uf (can also be called 'ufd' or 'mfd' - all mean EXACTLY the same thing.)

The voltage can be the same as the specified ones OR larger. The main thing you might find is the higher the voltage, sometimes the physical package size increases as well.

So a 4700mfd 25V cap could be replaced with a 4700mfd 35V (or 50V) without any concern.

Electrolytic caps (as these are) usually have a VERY wide tolerance and so are not particularly critical in any case for most pinball applications.