How do I check what kind of power supply I have in my computer?

Try using a volt meter, you could also take it to a shop they should tell you for free

it should have a label – sometimes visible without opening the case. Sometimes you have to open your case for that. Please do not open the power supply itself, because it is dangerous, even when the computer is unplugged.

only way I can tell on mine is if I open the case. if you still can’t see it that way, if there are bo marks at all its probably generic. best way would be voltmeter like the first response in this post

A voltmeter won’t tell you the peak wattage capacity.

If necessary you should be able to loosen up the power supply by removing just a few screws, usually from the back of the case. You shouldn’t have to disconnect anything, just move it around enough to find the label that will show you the peak wattage rating.

If you bought the unit whole then you should be able to find the specs for its power supply of your model number on the manufacturer’s web site.