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The dishwasher will most likely be hard wired if installed years ago, remove the bottom panel and verify flat romex cable is connected to be 100% sure.
But either way, since you are replacing a dishwasher and this is NOT a new circuit, you can still hard wire the new dishwasher.
You are not required to have a receptacle installed when replacing the appliance, only if you are installing a new circuit for one that you never had, do you need the upgrade to newer regulations.
Just shutdown the circuit breaker and make sure power is off, then unwire and remove. Install the new one and rewire and you are ready to go.
Let me know anything further,