Can I replace the power cord on an old electric drier, to fit my outlet?
If you mean that the cord has too many, or not enough prongs to fit in the receptacle.  You can buy the appropriate cord at any big box home improvement, hardware, or online store.  

Once you have the cord, search the internet for the manufacturer's documentation for the appliance.  Then follow the instructions for how to connect the new cord to the appliance.