Welcome. My name is ***** ***** would be glad to assist.
It sounds like, you are moving a dryer from a location that has a 4 prong receptacle, to a new location that was wired with a 3 prong receptacle.
This means the cord must be changed on the dryer.
If it is other than that, let me know the situation.
This is what you do on the new 3 wire cord.
The main power wires the same, the flat cor on 3 wire has it layed out properly, so the left wire goes to the left lug, center wire to center and right wire to right.
The difference is in the grounding.
Code grandfathered dryers and ranges for connecting to 3 wire receptacles.
INSIDE the dryer, you will ADD a short piece of wire from the CENTER lug and attach it to the green ground screw on the dryer frame whee the 4 wire cord had a green wire attached.
The dryer will ground through the neutral center connection to protect the frame from becoming energized.
See the below picture for reference:
Let me know anything further needed,