Answer: 5
Step-by-step explanation
The portion 25020 represents all of the sig figs. Any time we have zero between nonzero digits, that zero is significant. The trailing zero at the very end is also significant.
The first three zeros are not significant because 0.0025020 is the same as writing 2.5020 * 10^(-3)
Once the value is converted to scientific notation, it's much easier to spot the significant values.
There are 5 sig figs in 2.5020, so there are 5 sig figs in 0.0025020