What is the word for a Road Sign that shows direction

Solution 1:

Those are generally referred to as traffic signs or road signs:

• signs erected at the side of or above roads to give instructions or provide information to road users. The earliest signs were simple wooden or stone milestones. Later, signs with directional arms were introduced, for example, the fingerposts in the United Kingdom and their wooden counterparts in Saxony.

In your specific case you are probably referring to a:

direction sign,

• more fully defined as a direction, position, or indication sign by the Vienna Convention on Road Signs and Signals, is any road sign used primarily to give information about the location of either the driver or possible destinations, and are considered a subset of the informative signs group. Direction signs are far more varied internationally than other classes of sign, as the Vienna Convention does not specify sizes, colours, symbols or positions of such signs.

(Wikipedia)

Solution 2:

Note that traffic sign is a general-purpose term that includes hazard warnings, speed limits, etc.

A sign telling you which road to take to get somewhere (or telling you where you'll end up if you continue on your present course) is more specifically called a...

signpost - sign giving information such as the direction and distance to a nearby town, typically found at a road junction