Step 1: Chord length is \(6\) cm, so half chord is:
\[
\frac{6}{2}=3\text{ cm}
\]
Step 2: Distance from center to chord is:
\[
4\text{ cm}
\]
Step 3: Radius, half chord, and perpendicular distance form a right triangle.
\[
r^2=3^2+4^2
\]
\[
r^2=9+16=25
\]
\[
r=5\text{ cm}
\]
Step 4: Diameter is:
\[
2r=2(5)=10\text{ cm}
\]
\[
\boxed{10\text{ cm}}
\]