What you want in a power-supply is fairly straight forward. First of all, you want a good quality one. Not a grade-b Chinesium dollar store job, but a proper one. The connector should, of course, match the power input of your PI. For the RPi4 this would be a type USB-C.
Secondly you want the correct input voltage. For the PI this is 5(.x) volts.
For amperage, you just need to meet the minimum requirement. The RPi4 is specced for 3 amps. If your PSU is able to deliver more than that, that is okay.
A quick search shows that the switch adapter gets its max wattage from it's voltage range 5 to 15 and provides only 2.4 amps. This would mean that at 5v, it would not provide enough power in some scenarios.
I suggest to get a new PSU suitable for the unit.