ws2812b 5050 60 led per meter 300 led strip power issues
I think it's time you read the datasheet for the WorldSemi WS2812B.

You have to supply them with 5.0 Volts.  12 Volts will likely kill them, although because there's so many of these in parallel across the bus on such a long &amp; high-density string, you might've gotten lucky and had the 12V rail sag so much that they didn't see 12V for very long.

At full brightness (R, G &amp; B LEDs all 100% on) they'll draw 60mA, each.  So your 5V 100mA power supply won't power more than 1 of these WS2812Bs before buckling.  If that 5V/100mA PSU came with this bundle, it's probably only meant to power the controller you mention.

For a 300 x WS2812B strip you'll need a 5V 18 Amp PSU, and you'll need to connect this to at least both ends of the strip, and possibly half way along too, with THICK wires (AWG16 or thicker) because of the voltage-drop you'll get from an 18 Amp draw of a 5V rail along such a long strip with so many diodes.

WS2812B strips are utterly ubiquitous, and powering them has been documented ad nauseam all over the net.  Google is your friend.