Circuit for flashing LED strips controlled by Arduino Nano
Per the specifications of the SMD3528: You apply 12&nbsp;V to the strip. Each sub-group has three LEDs and a resistor.  

The power calculation is given as: Total power = (0.08&nbsp;W x LED_Quantity).
Or use 0.4 w x LED_Quantity for type SMD5630.

Using the total number of LEDs (LED_Quantity) calculate the total power, then divide by 12. This gives you required current (A).

So you will need a power supply with an output of 12&nbsp;V at (A) ampere.

If you plan on flashing these strips with an Arduino output a good method would be to use a MOSFET in the DC line powering the LEDs. The MOSFET would need to be rated for at least 10&nbsp;A. In place of a discrete MOSFET a similar rated solid-state DC relay module could be used. Solid-state relay modules often have opto-coupler inputs which are ideal for driving with an Arduino. If using a module be sure it is a DC type, not an AC type.