Most power supplies are "dumb" components. They provide electricity but do not transmit data like their name or wattage to the motherboard. Because of this, opening your case is the only 100% foolproof way to check.
Here’s a clear, step-by-step guide you can use or share: how to check what power supply you have
The only way to know the is to look at the sticker on the unit itself. Most power supplies are "dumb" components