Powering SMD 5050 strip via LM2596 DC/DC converter
LED strips work at \$12\, \mathrm{V}\$, but the individual chips do not. They are connected in groups of three with one series resistor. Voltage drop of one LED is around \$3.6\, \mathrm{V}\$, so the current is \$\dfrac{0.24}{3.6}\cong 65\, \mathrm{mA}\$. For 30 blocks, it is \$30\cdot 65 \cong 2\, \mathrm{A}\$.

LM2596 is quite ancient, you could do better with something like TPS54340 or even better, with synchronous buck regulator likeLT8614. Newer chips have higher switching frequecies, which means that you can use smaller inductors with fatter wire and also smaller capacitors.

With only one block attached, it will work just fine (although less advanced regulators will have lower efficiency).

If you connect too much LEDs, you will overload and overheat the regulator and it will employ its overtemperature protection.

Edit: LEDs are grouped by 3 like this: