if the e part of the reg is at the front, example e123abc, then it's a mark 3 escort. roughly mark 1 went from 1968 to 1975, mark 2 1975 to 1980 mark 3 1980 on. no mark 1 escort ghias were ever produced, the equivalent would have been the now rare 1300e.
E reg is on the change over between Mk3 and Mk4. If yours has the ridged rear lights and slatted front grill then its a Mk3. Smooth rear lights and the bonnet turns down at the front, its a Mk4.
as per previous posts, if the reg is E123 ABC, then it is a mk4. the changeover year between mk3 and mk4 was 1986. C plate cars were the last of the mk3s, although a miniscule amount were registered on D plates. without a shadow of a doubt, your car is a Mk4 - unless the reg number is ABC 123E, then its a Mk1 escort.