Diagnosis and troubleshooting

I guess you moved about 1 mile per hour to take the photo, but the car is stationery so will show 0mph.

 

Joking aside, what model car?

Does the needle move at all?

Does the tachometer move?

 

Older cars have a mechanical reduction gear drive off the gearbox wheel drive shaft. It's a cable in a flexible tube. So could have worked loose or snapped.

 

So you can investigate at the gearbox, or where this tube reaches back of speedo.