Find all positive integers $n$ such that we can put $n$ equal squares on the plane that their sides are horizontal and vertical and the shape after putting the squares has at least $3$ axises.
1. **Understanding the Problem:**
   We need to find all positive integers \( n \) such that we can arrange \( n \) equal squares on the plane with their sides parallel to the coordinate axes, and the resulting shape has at least 3 axes of symmetry.

2. **Analyzing the Symmetry:**
   - The axes of symmetry must map the line segments of the squares to other line segments.
   - Reflection doubles angles, so such a symmetry axis must be parallel to \( x=0 \), \( y=0 \), \( x=y \), or \( x=-y \).

3. **Considering the Intersection of Symmetry Axes:**
   - If we have three symmetry axes intersecting at a point \( P \), by suitable reflection, we find that we actually have four axes of symmetry, all passing through \( P \).
   - Let \( P \) be the origin. Any point \((a,b)\) except for the origin has an orbit of 8 or 4 under the action of reflection across these lines.

4. **Determining the Possible Values of \( n \):**
   - If \( n = 4k \), we can place the squares with centers at \((1,0), (2,0), \dots, (k,0), (-1,0), \dots, (-k,0)\) and \((0,1), \dots, (0,k), (0,-1), \dots, (0,-k)\).
   - For \( n = 4k+1 \), we add the square centered at \((0,0)\).

5. **Conclusion:**
   - The arrangement of squares ensures that the shape has at least 3 axes of symmetry.
   - Therefore, \( n \) must be congruent to \( 0 \) or \( 1 \) modulo 4.

The final answer is \( \boxed{ n \equiv 0 \pmod{4} } \) or \( n \equiv 1 \pmod{4} \).