I have a Tasco 3-9x40 scope. It has regular duplex with a 2nd vertical cross hair. Top turret/elevation has 100 - 500 increments. Also has readings where you adust the power for antelope,deer,elk etc.
Can anyone tell me about this scope and when were they made and are they any good.

Yours is a range finding scope. The stadia wires are set to approximate the 18" distance from the back to brisket of a whitetail deer. With the deer bracketed between the wires, the distance will be indicated by the index readings on the elevation turret. When you adjust for antelope (smaller) or elk (larger) the scope reticle adjustments will compensate for their smaller or larger dimensions from back to brisket.

These scopes came around aprox. 10-15 years ago.

Tasco scopes are in the lower economic price range. Some folks have good luck with them, some don't. All the Tasco's I formerly owned have been traded on trade rifles or sold for a pittance.

So I can adjust the 3-9 power like any other scope or only at the ranges that correlate to the yardage turret

You get your range by adjusting the power settings to bracket the animal. The yardage indicated is then dialed into the elevation turret to compensate for a dead-on hold for the range indicated..