At minimum, about 2,100 dinosaur fossils, probably not more than 200,000.
The main problem with this idea is that most of the dinosaur fossils are embedded in solid rock. While some are close to the surface, or even directly exposed by erosion, most are probably buried by literal tons of rock and sediments.
To give any sort of meaningful answer we have to make some assumptions about the magical forces and their upper limit.
Lets imagine that the magic force to hold up our dinosaur revenant can also remove at an equal amount of confining rock / sediment layer.
Some example numbers:
A 15 ton dinosaur might have a surface area of 10m^2 of rock covering it. Assume an average density of 2.6 g/cm^3 for quartz based rock, and our magic dino can escape from being buried about 1/2 m deep.
0.5m * 10m^2 * 2600kg/m^3 = 13,000kg of covering rock.
15 tons = 15 * 2000 lbs/ton / (2.2 lbs/ kg) = 13,636 kg of dinosaur
Larger dinosaurs would weigh more, but would also have a larger surface area to have to escape from, so it probably balances out.
I made a ton of wild assumptions here, such as a dinosaur fossil weighs about as much as the live dinosaur, rock types covering them, and surface area. This is just to get a decent idea of what we're dealing with.
Apply some hand-wavium to adjust the strength of the magic to extract them from even further down by magically shattering the rock and having the revived dinosaurs crawl upwards through the rubble. Three meters deep is probably a decent ballpark for that.
The exact number of remains in that region is difficult to predict because we don't know how many dinosaur fossils there are in total or their distribution.
However, it is estimated that there are around 2,100 fairly complete dinosaur skeletons in museums around the world. Those will be far easier to remove from their locations in research institutions than those locked in bedrock.
Lets work with that number and say we have found 10% of partially exposed dinosaur fossils world wide, and now we can say 20,000 dinosaurs are exhumed by our spell.
Adjust that percentage as you please (or how optimistic you might be for paleontologists!) and say that our 2,100 found skeletons are only 1% of the global total in our range of the surface and you've got 200,000 revived dinosaurs.
Here is the source I used for the number in museums: https://www.scholastic.com/teachers/articles/teaching-content/unearthing-dinosaur-bones-and-fossils/
Have fun and I hope that helped!