Does a 1991 Chevy lumina euro 4 door have a cord that you plug in to keep it warm if so where would it be located?

The block heater is optional.

If it equiped the plug in end of the cord should be in the left front or right front corner of the engine compartment. depends on engine and who installed the Block heater.

But a car this age if a replacement cord was ever fitted then your guess is as good as mine.

A hint: You are looking for a flat cord with three ribs for the three wires inside, it looks quite diferent than any other Automotive wire under the hood. Look at a freinds so you can see what I mean.