Ok, so as the title says i want to know if every psu would work on any motherboard you connect it to or is there a compatibility thingy?
If its the second one, will i be able to place any psu on my 042P49 motherboard or it is a bit old for that?
If that is a Dell Optiplex 3010 motherboard, you'll be fine with any modern PSU that physically fits the space in the case.
Dell has stayed with standard connections on their Optiplex line for a long time now. Some pre-builts however have proprietary connections that either require adapters or can't use a retail PSU at all.
It uses a standard ATX PSU. But you need one that has enough power for your specs and won't take up too much room in the case as room is limited in OEM cases.