Connect this to that without soldering using these quick terminal blocks. They allow connecting of two sets of four wires together using just a flat-head screwdriver. These are UL rated to carry up to 15 Amps, so they're great for high current LED strips! Can be used with wires from 14AWG to 22 AWG
Adafruit NeoPixel Digital RGB LED strips come to us in 4 or 5 meter reels with a 2 or 3-pin JST SM connector on each end and separated power/ground wires as shown in the pic below. If you order a full 4 or 5 meters, you get the full reel with both connectors installed (like the pic below).
If you buy less than a full reel, you'll get a single strip, but it will be a cut piece from a reel which may or may not have a connector on it. If the piece comes from the end of the reel, the connector may be on the output end of the strip!