3. Given that the ellipse $C_{1}$ and the hyperbola $C_{2}$ share foci $F_{1}(3,0), F_{2}(-3,0)$, and have coincident minor axes. Then the number of lattice points inside the region enclosed by the intersection points of $C_{1}$ and $C_{2}$ is $\qquad$

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3.25.

From the problem, we can let
$$
C_{1}: \frac{x^{2}}{m+9}+\frac{y^{2}}{m}=1, C_{2}: \frac{x^{2}}{9-m}-\frac{y^{2}}{m}=1,
$$

where $0<m<9$.
Let the intersection point be $P\left(x_{0}, y_{0}\right)$. Then, since point $P$ lies on $C_{1}$ and $C_{2}$, we have $\frac{x_{0}^{2}}{m+9}+\frac{x_{0}^{2}}{9-m}=2$, which simplifies to $x_{0}^{2}=9-\frac{m^{2}}{9}$.
Thus, $y_{0}^{2}=\frac{m^{2}}{9}$, where $x_{0}^{2}, y_{0}^{2} \neq 0,9$.
Therefore, $x_{0}^{2}+y_{0}^{2}=9$.
From the sketch (omitted), it is known that there are 25 lattice points within the enclosed region.