The Qwiic Connect System, which Sparkfun created and is popularizing, lets you connect multiple I2C devices together without having to solder connections to everything, removes the possiblity of connecting the wires incorrectly, and makes a mess of wires into a professional looking and neat product.
Each Qwiic device has a polarized 4-pin SMD female connector. The various wires have a male adapter, either on each end to connect multiple Qwiic devices, or on only one end. The other end is either a male or female dupont header connector (more commonly refered to as jumper wires).
Sparkfun has a few master devices that have a Qwiic connector already on the board, the Blackboard being the most notable. With that, you just need some Qwiic to Qwiic wires to connect all your Qwiic-compatible devices.
If your master device doesn’t have a connector, you’ll need to use a Male to Qwiic wire (the kind with pins you plug in to a female header), or a Female to Qwiic wire (the kind that plugs into something else).
All μFire boards come with two Qwiic connectors, this allows you to connect one to the other in a daisy-chain fashion. So figure out if you need a male/female to Qwiic wire to connect your master and μFire board, and then however many Qwiic to Qwiic wires you need to daisy-chain the rest together.
The I2C Sensor Isolator has a third connector that should be connected to whatever device you are keeping isolated, so don’t forget to add an extra wire, one on the INPUT side, and one on the ISO side.
You can buy all the wires you need through this website at the same price Sparkfun sells them.