I have outlet electric plugs from early 90's. Plugs are not GFCI and do not have the test / reset button. How do I reset.?

there's a central GFCI for each circuit that has one. look in breaker box. also look in the bathroom closest to the breaker box.

If overcurrent has caused the breaker to trip then you need to press the affected breaker completely to the off position before switching back on.

It is possible that they are fed through a GFCI that you haven't located yet, but it's likely that the heating and cooling expansion and contraction has caused a wire that was pushed into a stab-back receptacle to work loose. A common problem. All l the receptacles downstream from the loose wire will fail since the connection for those is through the outlet itself. You would need to unscrew all the non-working receptacles from their junction box and make sure the wires are completely pressed into the receptacle. If you don't find one that has loose wires then you will need to remove working receptacles to see if the power lead that feeds downstream receptacles has come loose. Sometimes the failure is bent wire spring in the outlet that holds the wire in the outlet. If you find an outlet with a loose wire it is a good idea to replace the receptacle with a new one.